OpenGL ES 2.0 GLSL 桶形失真着色器不工作
OpenGL ES 2.0 GLSL Barrel Distortion Shader not working
我从 OpenGL ES 2.0 教程中获取了代码：github。com/learnopengles/Learn-OpenGLES-Tutorials
并自定义 class "LessonOneRenderer" 以测试桶形失真着色器，如本网站所述：
www.geeks3d.com/20140213/glsl-shader-library-fish-eye-and-dome-and-barrel-distortion-post-processing-filters/2/
这是 "untouched" 没有调用 distort() 函数的结果：
http://fs1.directupload.net/images/150125/hw746rcn.png
调用函数的结果：
http://fs2.directupload.net/images/150125/f84arxoj.png
/**
* This class implements our custom renderer. Note that the GL10 parameter passed in is unused for OpenGL ES 2.0
* renderers -- the static class GLES20 is used instead.
*/
public class LessonOneRenderer implements GLSurfaceView.Renderer
{
/**
* Store the model matrix. This matrix is used to move models from object space (where each model can be thought
* of being located at the center of the universe) to world space.
*/
private float[] mModelMatrix = new float[16];
/**
* Store the view matrix. This can be thought of as our camera. This matrix transforms world space to eye space;
* it positions things relative to our eye.
*/
private float[] mViewMatrix = new float[16];
/** Store the projection matrix. This is used to project the scene onto a 2D viewport. */
private float[] mProjectionMatrix = new float[16];
/** Allocate storage for the final combined matrix. This will be passed into the shader program. */
private float[] mMVPMatrix = new float[16];
/** Store our model data in a float buffer. */
private final FloatBuffer mTriangle1Vertices;
/** This will be used to pass in the transformation matrix. */
private int mMVPMatrixHandle;
/** This will be used to pass in model position information. */
private int mPositionHandle;
/** This will be used to pass in model color information. */
private int mColorHandle;
/** How many bytes per float. */
private final int mBytesPerFloat = 4;
/** How many elements per vertex. */
private final int mStrideBytes = 7 * mBytesPerFloat;
/** Offset of the position data. */
private final int mPositionOffset = 0;
/** Size of the position data in elements. */
private final int mPositionDataSize = 3;
/** Offset of the color data. */
private final int mColorOffset = 3;
/** Size of the color data in elements. */
private final int mColorDataSize = 4;
private FloatBuffer vertexBuffer;
private ShortBuffer drawListBuffer;
// number of coordinates per vertex in this array
static final int COORDS_PER_VERTEX = 3;
// X Y Z
static float squareCoords[] = { -0.5f, 0.5f, 0.0f, // top left
-0.5f, -0.5f, 0.0f, // bottom left
0.5f, -0.5f, 0.0f, // bottom right
0.5f, 0.5f, 0.0f }; // top right
private short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices
float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 1.0f };
static final int vertexStride = COORDS_PER_VERTEX * 4;
static final int vertexCount = 4;
private ByteBuffer dlb;
/**
* Initialize the model data.
*/
public LessonOneRenderer()
{
ByteBuffer bb = ByteBuffer.allocateDirect(squareCoords.length * 4); // (# of coordinate values * 4 bytes per float)
bb.order(ByteOrder.nativeOrder());
vertexBuffer = bb.asFloatBuffer();
vertexBuffer.put(squareCoords);
vertexBuffer.position(0);
// initialize byte buffer for the draw list
ByteBuffer dlb = ByteBuffer.allocateDirect(drawOrder.length * 2); // (# of coordinate values * 2 bytes per short)
dlb.order(ByteOrder.nativeOrder());
drawListBuffer = dlb.asShortBuffer();
drawListBuffer.put(drawOrder);
drawListBuffer.position(0);
// Define points for equilateral triangles.
// This triangle is red, green, and blue.
final float[] triangle1VerticesData = {
// X, Y, Z,
// R, G, B, A
-0.5f, 0.5f, 0.0f, // top left
1.0f, 0.0f, 0.0f, 1.0f,
-0.5f, -0.5f, 0.0f,// bottom left
0.0f, 0.0f, 1.0f, 1.0f,
0.5f, -0.5f, 0.0f, // bottom right
0.0f, 1.0f, 0.0f, 1.0f
,
0.5f, 0.5f, 0.0f, // top right
0.0f, 1.0f, 0.0f, 1.0f
};
// Initialize the buffers.
mTriangle1Vertices = ByteBuffer.allocateDirect(triangle1VerticesData.length * mBytesPerFloat)
.order(ByteOrder.nativeOrder()).asFloatBuffer();
mTriangle1Vertices.put(triangle1VerticesData).position(0);
// initialize byte buffer for the draw list
dlb = ByteBuffer.allocateDirect(drawOrder.length * 2); // (# of coordinate values * 2 bytes per short)
dlb.order(ByteOrder.nativeOrder());
drawListBuffer = dlb.asShortBuffer();
drawListBuffer.put(drawOrder);
drawListBuffer.position(0);
}
@Override
public void onSurfaceCreated(GL10 glUnused, EGLConfig config)
{
// Set the background clear color to gray.
GLES20.glClearColor(0.5f, 0.5f, 0.5f, 0.5f);
// Position the eye behind the origin.
final float eyeX = 0.0f;
final float eyeY = 0.0f;
final float eyeZ = 1.5f;
// We are looking toward the distance
final float lookX = 0.0f;
final float lookY = 0.0f;
final float lookZ = -5.0f;
// Set our up vector. This is where our head would be pointing were we holding the camera.
final float upX = 0.0f;
final float upY = 1.0f;
final float upZ = 0.0f;
// Set the view matrix. This matrix can be said to represent the camera position.
// NOTE: In OpenGL 1, a ModelView matrix is used, which is a combination of a model and
// view matrix. In OpenGL 2, we can keep track of these matrices separately if we choose.
Matrix.setLookAtM(mViewMatrix, 0, eyeX, eyeY, eyeZ, lookX, lookY, lookZ, upX, upY, upZ);
final String vertexShader =
"uniform mat4 u_MVPMatrix; \n" // A constant representing the combined model/view/projection matrix.
+ "attribute vec4 a_Position; \n" // Per-vertex position information we will pass in.
+ "attribute vec4 a_Color; \n" // Per-vertex color information we will pass in.
+ "varying vec4 a_Pos; \n"
+ "varying vec4 v_Color; \n" // This will be passed into the fragment shader.
+" "
+"vec4 Distort(vec4 p){ \n"
+" float BarrelPower = 0.4; \n"
+" vec2 v = p.xy / p.w; \n"
+" float radius = length(v); \n"
+" if (radius > 0.0){ \n"
+" float theta = atan(v.y,v.x); \n"
+" radius = pow(radius, BarrelPower);\n"
+" v.x = radius * cos(theta); \n"
+" v.y = radius * sin(theta); \n"
+" p.xy = v.xy * p.w; \n"
+" }"
+" \n"
+" return p; \n"
+" } \n"
+ "void main() \n" // The entry point for our vertex shader.
+ "{ \n"
+ " v_Color = a_Color; \n" // Pass the color through to the fragment shader.
+ " vec4 P = u_MVPMatrix * a_Position;" // It will be interpolated across the triangle.
+ " gl_Position = Distort(P); \n" // gl_Position is a special variable used to store the final position.
+ " \n" // Multiply the vertex by the matrix to get the final point in
+ "} \n"; // normalized screen coordinates.
final String fragmentShader =
// Set the default precision to medium. We don't need as high of a
"varying vec4 a_Pos;" // precision in the fragment shader.
+ "varying vec4 v_Color; \n" // This is the color from the vertex shader interpolated across the
// triangle per fragment.
+ "void main() \n" // The entry point for our fragment shader.
+ "{ vec4 c = vec4(1.0); \n"
+ " gl_FragColor = v_Color; \n" // Pass the color directly through the pipeline.
+ "} \n";
// Load in the vertex shader.
int vertexShaderHandle = GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER);
if (vertexShaderHandle != 0)
{
// Pass in the shader source.
GLES20.glShaderSource(vertexShaderHandle, vertexShader);
// Compile the shader.
GLES20.glCompileShader(vertexShaderHandle);
// Get the compilation status.
final int[] compileStatus = new int[1];
GLES20.glGetShaderiv(vertexShaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
// If the compilation failed, delete the shader.
if (compileStatus[0] == 0)
{
GLES20.glDeleteShader(vertexShaderHandle);
vertexShaderHandle = 0;
}
}
if (vertexShaderHandle == 0)
{
throw new RuntimeException("Error creating vertex shader.");
}
// Load in the fragment shader shader.
int fragmentShaderHandle = GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER);
if (fragmentShaderHandle != 0)
{
// Pass in the shader source.
GLES20.glShaderSource(fragmentShaderHandle, fragmentShader);
// Compile the shader.
GLES20.glCompileShader(fragmentShaderHandle);
// Get the compilation status.
final int[] compileStatus = new int[1];
GLES20.glGetShaderiv(fragmentShaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
// If the compilation failed, delete the shader.
if (compileStatus[0] == 0)
{
GLES20.glDeleteShader(fragmentShaderHandle);
fragmentShaderHandle = 0;
}
}
if (fragmentShaderHandle == 0)
{
throw new RuntimeException("Error creating fragment shader.");
}
// Create a program object and store the handle to it.
int programHandle = GLES20.glCreateProgram();
if (programHandle != 0)
{
// Bind the vertex shader to the program.
GLES20.glAttachShader(programHandle, vertexShaderHandle);
// Bind the fragment shader to the program.
GLES20.glAttachShader(programHandle, fragmentShaderHandle);
// Bind attributes
GLES20.glBindAttribLocation(programHandle, 0, "a_Position");
GLES20.glBindAttribLocation(programHandle, 1, "a_Color");
// Link the two shaders together into a program.
GLES20.glLinkProgram(programHandle);
// Get the link status.
final int[] linkStatus = new int[1];
GLES20.glGetProgramiv(programHandle, GLES20.GL_LINK_STATUS, linkStatus, 0);
// If the link failed, delete the program.
if (linkStatus[0] == 0)
{
GLES20.glDeleteProgram(programHandle);
programHandle = 0;
}
}
if (programHandle == 0)
{
throw new RuntimeException("Error creating program.");
}
// Set program handles. These will later be used to pass in values to the program.
mMVPMatrixHandle = GLES20.glGetUniformLocation(programHandle, "u_MVPMatrix");
mPositionHandle = GLES20.glGetAttribLocation(programHandle, "a_Position");
mColorHandle = GLES20.glGetAttribLocation(programHandle, "a_Color");
// Tell OpenGL to use this program when rendering.
GLES20.glUseProgram(programHandle);
}
@Override
public void onSurfaceChanged(GL10 glUnused, int width, int height)
{
// Set the OpenGL viewport to the same size as the surface.
GLES20.glViewport(0, 0, width, height);
// Create a new perspective projection matrix. The height will stay the same
// while the width will vary as per aspect ratio.
final float ratio = (float) width / height;
final float left = -ratio;
final float right = ratio;
final float bottom = -1.0f;
final float top = 1.0f;
final float near = 1.0f;
final float far = 10.0f;
Matrix.frustumM(mProjectionMatrix, 0, left, right, bottom, top, near, far);
}
@Override
public void onDrawFrame(GL10 glUnused)
{
GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);
// Do a complete rotation every 10 seconds.
long time = SystemClock.uptimeMillis() % 10000L;
float angleInDegrees = (360.0f / 10000.0f) * ((int) time);
// Draw the triangle facing straight on.
//Matrix.setIdentityM(mModelMatrix, 0);
//Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);
//drawTriangle(mTriangle1Vertices);
//Draw Square
Matrix.setIdentityM(mModelMatrix, 0);
Matrix.translateM(mModelMatrix, 0, 0.0f, -0.7f, 0.0f);
//Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);
this.drawSquare(mTriangle1Vertices);
//Draw Square
Matrix.setIdentityM(mModelMatrix, 0);
Matrix.translateM(mModelMatrix, 0, 0.0f, 0.7f, 0.0f);
//Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);
this.drawSquare(mTriangle1Vertices);
// Draw one translated a bit down and rotated to be flat on the ground.
//Matrix.setIdentityM(mModelMatrix, 0);
//Matrix.translateM(mModelMatrix, 0, 0.0f, -1.0f, 0.0f);
//Matrix.rotateM(mModelMatrix, 0, 90.0f, 1.0f, 0.0f, 0.0f);
//Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);
//drawTriangle(mTriangle2Vertices);
// Draw one translated a bit to the right and rotated to be facing to the left.
//Matrix.setIdentityM(mModelMatrix, 0);
//Matrix.translateM(mModelMatrix, 0, 1.0f, 0.0f, 0.0f);
//Matrix.rotateM(mModelMatrix, 0, 90.0f, 0.0f, 1.0f, 0.0f);
//Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);
//drawTriangle(mTriangle3Vertices);
// test.draw();
}
/**
* Draws a triangle from the given vertex data.
*
* @param aTriangleBuffer The buffer containing the vertex data.
*/
private void drawTriangle(final FloatBuffer aTriangleBuffer)
{
// Pass in the position information
aTriangleBuffer.position(mPositionOffset);
GLES20.glVertexAttribPointer(mPositionHandle, mPositionDataSize, GLES20.GL_FLOAT, false,
mStrideBytes, aTriangleBuffer);
GLES20.glEnableVertexAttribArray(mPositionHandle);
// Pass in the color information
aTriangleBuffer.position(mColorOffset);
GLES20.glVertexAttribPointer(mColorHandle, mColorDataSize, GLES20.GL_FLOAT, false,
mStrideBytes, aTriangleBuffer);
GLES20.glEnableVertexAttribArray(mColorHandle);
// This multiplies the view matrix by the model matrix, and stores the result in the MVP matrix
// (which currently contains model * view).
Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
// This multiplies the modelview matrix by the projection matrix, and stores the result in the MVP matrix
// (which now contains model * view * projection).
Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0);
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 3);
}
private void drawSquare(final FloatBuffer aTriangleBuffer)
{
// Pass in the position information
aTriangleBuffer.position(mPositionOffset);
GLES20.glVertexAttribPointer(mPositionHandle, mPositionDataSize, GLES20.GL_FLOAT, false,
mStrideBytes, aTriangleBuffer);
GLES20.glEnableVertexAttribArray(mPositionHandle);
// Pass in the color information
aTriangleBuffer.position(mColorOffset);
GLES20.glVertexAttribPointer(mColorHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false,
vertexStride, aTriangleBuffer);
GLES20.glEnableVertexAttribArray(mColorHandle);
// This multiplies the view matrix by the model matrix, and stores the result in the MVP matrix
// (which currently contains model * view).
Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
// This multiplies the modelview matrix by the projection matrix, and stores the result in the MVP matrix
// (which now contains model * view * projection).
Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0);
GLES20.glDrawArrays(GLES20.GL_TRIANGLE_FAN, 0, 4);
}
}
有人知道我缺少什么来扭曲示例中的正方形吗？
您在顶点着色器中应用扭曲效果。所以你所做的就是移动这些球体的 4 个角。这样达不到你想要的效果。
有三种不同的选择。理论上你可以为你的正方形使用一些更高的细分，所以你只需创建一个 2D 顶点网格，然后可以根据失真单独移动它。如果您的网格足够精细，则该近似值的分段线性性质将不再可见。
但是，通常以不同的方式完成此类效果。人们通常不会针对特定效果调整几何模型。这种扭曲通常应用于 screen-space，作为 post-processing 效果（以及 link 你 post ed 正是这样做的）。这个想法是你可以将整个场景渲染成一个纹理，并绘制一个填充整个屏幕的单一纹理矩形作为最后的通道。在该通道中，您可以在片段着色器中将变形应用于纹理坐标，就像在原始示例中一样。
所有这些也可以在 OpenGL ES 中完成。要查找的关键字是 RTT（渲染到纹理）和 FBO（帧缓冲区对象）。在 GLES 上，此功能作为 OES_framebuffer_object 扩展提供（在大多数 ES 实现中得到广泛支持）。
但是，使用这些东西肯定比某些教程的典型 "lessson 1" 更高级，您可能想在尝试之前先阅读一些其他课程...;)
我从 OpenGL ES 2.0 教程中获取了代码：github。com/learnopengles/Learn-OpenGLES-Tutorials
并自定义 class "LessonOneRenderer" 以测试桶形失真着色器，如本网站所述：
www.geeks3d.com/20140213/glsl-shader-library-fish-eye-and-dome-and-barrel-distortion-post-processing-filters/2/
这是 "untouched" 没有调用 distort() 函数的结果：
http://fs1.directupload.net/images/150125/hw746rcn.png
调用函数的结果：
http://fs2.directupload.net/images/150125/f84arxoj.png
/**
* This class implements our custom renderer. Note that the GL10 parameter passed in is unused for OpenGL ES 2.0
* renderers -- the static class GLES20 is used instead.
*/
public class LessonOneRenderer implements GLSurfaceView.Renderer
{
/**
* Store the model matrix. This matrix is used to move models from object space (where each model can be thought
* of being located at the center of the universe) to world space.
*/
private float[] mModelMatrix = new float[16];
/**
* Store the view matrix. This can be thought of as our camera. This matrix transforms world space to eye space;
* it positions things relative to our eye.
*/
private float[] mViewMatrix = new float[16];
/** Store the projection matrix. This is used to project the scene onto a 2D viewport. */
private float[] mProjectionMatrix = new float[16];
/** Allocate storage for the final combined matrix. This will be passed into the shader program. */
private float[] mMVPMatrix = new float[16];
/** Store our model data in a float buffer. */
private final FloatBuffer mTriangle1Vertices;
/** This will be used to pass in the transformation matrix. */
private int mMVPMatrixHandle;
/** This will be used to pass in model position information. */
private int mPositionHandle;
/** This will be used to pass in model color information. */
private int mColorHandle;
/** How many bytes per float. */
private final int mBytesPerFloat = 4;
/** How many elements per vertex. */
private final int mStrideBytes = 7 * mBytesPerFloat;
/** Offset of the position data. */
private final int mPositionOffset = 0;
/** Size of the position data in elements. */
private final int mPositionDataSize = 3;
/** Offset of the color data. */
private final int mColorOffset = 3;
/** Size of the color data in elements. */
private final int mColorDataSize = 4;
private FloatBuffer vertexBuffer;
private ShortBuffer drawListBuffer;
// number of coordinates per vertex in this array
static final int COORDS_PER_VERTEX = 3;
// X Y Z
static float squareCoords[] = { -0.5f, 0.5f, 0.0f, // top left
-0.5f, -0.5f, 0.0f, // bottom left
0.5f, -0.5f, 0.0f, // bottom right
0.5f, 0.5f, 0.0f }; // top right
private short drawOrder[] = { 0, 1, 2, 0, 2, 3 }; // order to draw vertices
float color[] = { 0.63671875f, 0.76953125f, 0.22265625f, 1.0f };
static final int vertexStride = COORDS_PER_VERTEX * 4;
static final int vertexCount = 4;
private ByteBuffer dlb;
/**
* Initialize the model data.
*/
public LessonOneRenderer()
{
ByteBuffer bb = ByteBuffer.allocateDirect(squareCoords.length * 4); // (# of coordinate values * 4 bytes per float)
bb.order(ByteOrder.nativeOrder());
vertexBuffer = bb.asFloatBuffer();
vertexBuffer.put(squareCoords);
vertexBuffer.position(0);
// initialize byte buffer for the draw list
ByteBuffer dlb = ByteBuffer.allocateDirect(drawOrder.length * 2); // (# of coordinate values * 2 bytes per short)
dlb.order(ByteOrder.nativeOrder());
drawListBuffer = dlb.asShortBuffer();
drawListBuffer.put(drawOrder);
drawListBuffer.position(0);
// Define points for equilateral triangles.
// This triangle is red, green, and blue.
final float[] triangle1VerticesData = {
// X, Y, Z,
// R, G, B, A
-0.5f, 0.5f, 0.0f, // top left
1.0f, 0.0f, 0.0f, 1.0f,
-0.5f, -0.5f, 0.0f,// bottom left
0.0f, 0.0f, 1.0f, 1.0f,
0.5f, -0.5f, 0.0f, // bottom right
0.0f, 1.0f, 0.0f, 1.0f
,
0.5f, 0.5f, 0.0f, // top right
0.0f, 1.0f, 0.0f, 1.0f
};
// Initialize the buffers.
mTriangle1Vertices = ByteBuffer.allocateDirect(triangle1VerticesData.length * mBytesPerFloat)
.order(ByteOrder.nativeOrder()).asFloatBuffer();
mTriangle1Vertices.put(triangle1VerticesData).position(0);
// initialize byte buffer for the draw list
dlb = ByteBuffer.allocateDirect(drawOrder.length * 2); // (# of coordinate values * 2 bytes per short)
dlb.order(ByteOrder.nativeOrder());
drawListBuffer = dlb.asShortBuffer();
drawListBuffer.put(drawOrder);
drawListBuffer.position(0);
}
@Override
public void onSurfaceCreated(GL10 glUnused, EGLConfig config)
{
// Set the background clear color to gray.
GLES20.glClearColor(0.5f, 0.5f, 0.5f, 0.5f);
// Position the eye behind the origin.
final float eyeX = 0.0f;
final float eyeY = 0.0f;
final float eyeZ = 1.5f;
// We are looking toward the distance
final float lookX = 0.0f;
final float lookY = 0.0f;
final float lookZ = -5.0f;
// Set our up vector. This is where our head would be pointing were we holding the camera.
final float upX = 0.0f;
final float upY = 1.0f;
final float upZ = 0.0f;
// Set the view matrix. This matrix can be said to represent the camera position.
// NOTE: In OpenGL 1, a ModelView matrix is used, which is a combination of a model and
// view matrix. In OpenGL 2, we can keep track of these matrices separately if we choose.
Matrix.setLookAtM(mViewMatrix, 0, eyeX, eyeY, eyeZ, lookX, lookY, lookZ, upX, upY, upZ);
final String vertexShader =
"uniform mat4 u_MVPMatrix; \n" // A constant representing the combined model/view/projection matrix.
+ "attribute vec4 a_Position; \n" // Per-vertex position information we will pass in.
+ "attribute vec4 a_Color; \n" // Per-vertex color information we will pass in.
+ "varying vec4 a_Pos; \n"
+ "varying vec4 v_Color; \n" // This will be passed into the fragment shader.
+" "
+"vec4 Distort(vec4 p){ \n"
+" float BarrelPower = 0.4; \n"
+" vec2 v = p.xy / p.w; \n"
+" float radius = length(v); \n"
+" if (radius > 0.0){ \n"
+" float theta = atan(v.y,v.x); \n"
+" radius = pow(radius, BarrelPower);\n"
+" v.x = radius * cos(theta); \n"
+" v.y = radius * sin(theta); \n"
+" p.xy = v.xy * p.w; \n"
+" }"
+" \n"
+" return p; \n"
+" } \n"
+ "void main() \n" // The entry point for our vertex shader.
+ "{ \n"
+ " v_Color = a_Color; \n" // Pass the color through to the fragment shader.
+ " vec4 P = u_MVPMatrix * a_Position;" // It will be interpolated across the triangle.
+ " gl_Position = Distort(P); \n" // gl_Position is a special variable used to store the final position.
+ " \n" // Multiply the vertex by the matrix to get the final point in
+ "} \n"; // normalized screen coordinates.
final String fragmentShader =
// Set the default precision to medium. We don't need as high of a
"varying vec4 a_Pos;" // precision in the fragment shader.
+ "varying vec4 v_Color; \n" // This is the color from the vertex shader interpolated across the
// triangle per fragment.
+ "void main() \n" // The entry point for our fragment shader.
+ "{ vec4 c = vec4(1.0); \n"
+ " gl_FragColor = v_Color; \n" // Pass the color directly through the pipeline.
+ "} \n";
// Load in the vertex shader.
int vertexShaderHandle = GLES20.glCreateShader(GLES20.GL_VERTEX_SHADER);
if (vertexShaderHandle != 0)
{
// Pass in the shader source.
GLES20.glShaderSource(vertexShaderHandle, vertexShader);
// Compile the shader.
GLES20.glCompileShader(vertexShaderHandle);
// Get the compilation status.
final int[] compileStatus = new int[1];
GLES20.glGetShaderiv(vertexShaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
// If the compilation failed, delete the shader.
if (compileStatus[0] == 0)
{
GLES20.glDeleteShader(vertexShaderHandle);
vertexShaderHandle = 0;
}
}
if (vertexShaderHandle == 0)
{
throw new RuntimeException("Error creating vertex shader.");
}
// Load in the fragment shader shader.
int fragmentShaderHandle = GLES20.glCreateShader(GLES20.GL_FRAGMENT_SHADER);
if (fragmentShaderHandle != 0)
{
// Pass in the shader source.
GLES20.glShaderSource(fragmentShaderHandle, fragmentShader);
// Compile the shader.
GLES20.glCompileShader(fragmentShaderHandle);
// Get the compilation status.
final int[] compileStatus = new int[1];
GLES20.glGetShaderiv(fragmentShaderHandle, GLES20.GL_COMPILE_STATUS, compileStatus, 0);
// If the compilation failed, delete the shader.
if (compileStatus[0] == 0)
{
GLES20.glDeleteShader(fragmentShaderHandle);
fragmentShaderHandle = 0;
}
}
if (fragmentShaderHandle == 0)
{
throw new RuntimeException("Error creating fragment shader.");
}
// Create a program object and store the handle to it.
int programHandle = GLES20.glCreateProgram();
if (programHandle != 0)
{
// Bind the vertex shader to the program.
GLES20.glAttachShader(programHandle, vertexShaderHandle);
// Bind the fragment shader to the program.
GLES20.glAttachShader(programHandle, fragmentShaderHandle);
// Bind attributes
GLES20.glBindAttribLocation(programHandle, 0, "a_Position");
GLES20.glBindAttribLocation(programHandle, 1, "a_Color");
// Link the two shaders together into a program.
GLES20.glLinkProgram(programHandle);
// Get the link status.
final int[] linkStatus = new int[1];
GLES20.glGetProgramiv(programHandle, GLES20.GL_LINK_STATUS, linkStatus, 0);
// If the link failed, delete the program.
if (linkStatus[0] == 0)
{
GLES20.glDeleteProgram(programHandle);
programHandle = 0;
}
}
if (programHandle == 0)
{
throw new RuntimeException("Error creating program.");
}
// Set program handles. These will later be used to pass in values to the program.
mMVPMatrixHandle = GLES20.glGetUniformLocation(programHandle, "u_MVPMatrix");
mPositionHandle = GLES20.glGetAttribLocation(programHandle, "a_Position");
mColorHandle = GLES20.glGetAttribLocation(programHandle, "a_Color");
// Tell OpenGL to use this program when rendering.
GLES20.glUseProgram(programHandle);
}
@Override
public void onSurfaceChanged(GL10 glUnused, int width, int height)
{
// Set the OpenGL viewport to the same size as the surface.
GLES20.glViewport(0, 0, width, height);
// Create a new perspective projection matrix. The height will stay the same
// while the width will vary as per aspect ratio.
final float ratio = (float) width / height;
final float left = -ratio;
final float right = ratio;
final float bottom = -1.0f;
final float top = 1.0f;
final float near = 1.0f;
final float far = 10.0f;
Matrix.frustumM(mProjectionMatrix, 0, left, right, bottom, top, near, far);
}
@Override
public void onDrawFrame(GL10 glUnused)
{
GLES20.glClear(GLES20.GL_DEPTH_BUFFER_BIT | GLES20.GL_COLOR_BUFFER_BIT);
// Do a complete rotation every 10 seconds.
long time = SystemClock.uptimeMillis() % 10000L;
float angleInDegrees = (360.0f / 10000.0f) * ((int) time);
// Draw the triangle facing straight on.
//Matrix.setIdentityM(mModelMatrix, 0);
//Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);
//drawTriangle(mTriangle1Vertices);
//Draw Square
Matrix.setIdentityM(mModelMatrix, 0);
Matrix.translateM(mModelMatrix, 0, 0.0f, -0.7f, 0.0f);
//Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);
this.drawSquare(mTriangle1Vertices);
//Draw Square
Matrix.setIdentityM(mModelMatrix, 0);
Matrix.translateM(mModelMatrix, 0, 0.0f, 0.7f, 0.0f);
//Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);
this.drawSquare(mTriangle1Vertices);
// Draw one translated a bit down and rotated to be flat on the ground.
//Matrix.setIdentityM(mModelMatrix, 0);
//Matrix.translateM(mModelMatrix, 0, 0.0f, -1.0f, 0.0f);
//Matrix.rotateM(mModelMatrix, 0, 90.0f, 1.0f, 0.0f, 0.0f);
//Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);
//drawTriangle(mTriangle2Vertices);
// Draw one translated a bit to the right and rotated to be facing to the left.
//Matrix.setIdentityM(mModelMatrix, 0);
//Matrix.translateM(mModelMatrix, 0, 1.0f, 0.0f, 0.0f);
//Matrix.rotateM(mModelMatrix, 0, 90.0f, 0.0f, 1.0f, 0.0f);
//Matrix.rotateM(mModelMatrix, 0, angleInDegrees, 0.0f, 0.0f, 1.0f);
//drawTriangle(mTriangle3Vertices);
// test.draw();
}
/**
* Draws a triangle from the given vertex data.
*
* @param aTriangleBuffer The buffer containing the vertex data.
*/
private void drawTriangle(final FloatBuffer aTriangleBuffer)
{
// Pass in the position information
aTriangleBuffer.position(mPositionOffset);
GLES20.glVertexAttribPointer(mPositionHandle, mPositionDataSize, GLES20.GL_FLOAT, false,
mStrideBytes, aTriangleBuffer);
GLES20.glEnableVertexAttribArray(mPositionHandle);
// Pass in the color information
aTriangleBuffer.position(mColorOffset);
GLES20.glVertexAttribPointer(mColorHandle, mColorDataSize, GLES20.GL_FLOAT, false,
mStrideBytes, aTriangleBuffer);
GLES20.glEnableVertexAttribArray(mColorHandle);
// This multiplies the view matrix by the model matrix, and stores the result in the MVP matrix
// (which currently contains model * view).
Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
// This multiplies the modelview matrix by the projection matrix, and stores the result in the MVP matrix
// (which now contains model * view * projection).
Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0);
GLES20.glDrawArrays(GLES20.GL_TRIANGLES, 0, 3);
}
private void drawSquare(final FloatBuffer aTriangleBuffer)
{
// Pass in the position information
aTriangleBuffer.position(mPositionOffset);
GLES20.glVertexAttribPointer(mPositionHandle, mPositionDataSize, GLES20.GL_FLOAT, false,
mStrideBytes, aTriangleBuffer);
GLES20.glEnableVertexAttribArray(mPositionHandle);
// Pass in the color information
aTriangleBuffer.position(mColorOffset);
GLES20.glVertexAttribPointer(mColorHandle, COORDS_PER_VERTEX, GLES20.GL_FLOAT, false,
vertexStride, aTriangleBuffer);
GLES20.glEnableVertexAttribArray(mColorHandle);
// This multiplies the view matrix by the model matrix, and stores the result in the MVP matrix
// (which currently contains model * view).
Matrix.multiplyMM(mMVPMatrix, 0, mViewMatrix, 0, mModelMatrix, 0);
// This multiplies the modelview matrix by the projection matrix, and stores the result in the MVP matrix
// (which now contains model * view * projection).
Matrix.multiplyMM(mMVPMatrix, 0, mProjectionMatrix, 0, mMVPMatrix, 0);
GLES20.glUniformMatrix4fv(mMVPMatrixHandle, 1, false, mMVPMatrix, 0);
GLES20.glDrawArrays(GLES20.GL_TRIANGLE_FAN, 0, 4);
}
}
有人知道我缺少什么来扭曲示例中的正方形吗？
您在顶点着色器中应用扭曲效果。所以你所做的就是移动这些球体的 4 个角。这样达不到你想要的效果。
有三种不同的选择。理论上你可以为你的正方形使用一些更高的细分，所以你只需创建一个 2D 顶点网格，然后可以根据失真单独移动它。如果您的网格足够精细，则该近似值的分段线性性质将不再可见。
但是，通常以不同的方式完成此类效果。人们通常不会针对特定效果调整几何模型。这种扭曲通常应用于 screen-space，作为 post-processing 效果（以及 link 你 post ed 正是这样做的）。这个想法是你可以将整个场景渲染成一个纹理，并绘制一个填充整个屏幕的单一纹理矩形作为最后的通道。在该通道中，您可以在片段着色器中将变形应用于纹理坐标，就像在原始示例中一样。
所有这些也可以在 OpenGL ES 中完成。要查找的关键字是 RTT（渲染到纹理）和 FBO（帧缓冲区对象）。在 GLES 上，此功能作为 OES_framebuffer_object 扩展提供（在大多数 ES 实现中得到广泛支持）。
但是，使用这些东西肯定比某些教程的典型 "lessson 1" 更高级，您可能想在尝试之前先阅读一些其他课程...;)