Opengl OpenTK - 绘制深度缓冲区时出现白屏

Question

我目前正在尝试使用阴影贴图向我的 3D 引擎添加阴影。

首先，我从光的角度渲染场景，并将深度值保存在纹理中。然后我使用默认的 FBO 从纹理中绘制。就像在 this 教程中一样。问题是无论我移动到哪里，我的屏幕都是白色的。

GL.GetError() 输出 noError 并且我在顶点着色器中使用的 SSBO 具有正确的值。 GL.CheckFramebufferStatus() returns FramebufferCompleteExt.

这就是我为深度值创建 FBO 的方式：

_depthMapFBO = GL.GenFramebuffer();
_depthMapFBOColorBuffer = BufferObjects.FBO_TextureAttachment(_depthMapFBO, PixelInternalFormat.DepthComponent, PixelFormat.DepthComponent, FramebufferAttachment.DepthAttachment, 1024, 1024);
GL.BindFramebuffer(FramebufferTarget.Framebuffer, _depthMapFBO);
GL.DrawBuffer(DrawBufferMode.None);
GL.ReadBuffer(ReadBufferMode.None);

====================================

public static int FBO_TextureAttachment(int FrameBuffer, PixelInternalFormat PixelInternalFormat, PixelFormat PixelFormat, FramebufferAttachment FramebufferAttachment, int Width, int Height)
{
    // PixelInternalFormat = DepthComponent && PixelFormat = DepthComponent && FramebufferAttachment = DepthAttachment && Width, Height = 1024, 

    GL.BindFramebuffer(FramebufferTarget.Framebuffer, FrameBuffer);
    int _texture = GL.GenTexture();
            
    GL.BindTexture(TextureTarget.Texture2D, _texture);
    GL.TexImage2D(TextureTarget.Texture2D, 0, PixelInternalFormat, Width, Height, 0, PixelFormat, PixelType.Float, IntPtr.Zero);

    GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMinFilter, (int)All.Nearest);
    GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureMagFilter, (int)All.Nearest);
    GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapS, (int)All.Repeat);
    GL.TexParameter(TextureTarget.Texture2D, TextureParameterName.TextureWrapT, (int)All.Repeat);

    GL.FramebufferTexture2D(FramebufferTarget.Framebuffer, FramebufferAttachment, TextureTarget.Texture2D, _texture, 0);
    return _texture;
}

在我的渲染函数中它看起来像这样：

GL.BindFramebuffer(FramebufferTarget.Framebuffer, _depthMapFBO);
GL.Clear(ClearBufferMask.DepthBufferBit);

GL.Viewport(0, 0, 1024, 1024);
_simpleDepthProgram.Use();

float _nearPlane = 1.0f, _farPlane = 100f;
_lightProjection = Matrix4.CreateOrthographicOffCenter(-100.0f, 100.0f, -100.0f, 100.0f, _nearPlane, _farPlane);
_ligthView = Matrix4.LookAt(_allLamps[0].Position, new Vector3(0f), new Vector3(0.0f, 1.0f, 0.0f));

_lightSpaceMatrix = _lightProjection * _ligthView;
GL.UniformMatrix4(21, false, ref _lightSpaceMatrix);

// Copy all SSBO's 

GL.ActiveTexture(TextureUnit.Texture2);
GL.BindTexture(TextureTarget.Texture2D, _depthMapFBOColorBuffer);
Scene();

以及我绘制深度图的着色器：

#version 450 core
out vec4 FragColor;

uniform sampler2D scene;
uniform sampler2D bloomed;
uniform sampler2D depthMap;

uniform float zNear;
uniform float zFar;

float LinearizeDepth(float depth)
{
    float z = depth * 2.0 - 1.0; // Back to NDC 
    return (2.0 * zNear * zFar) / (zFar + zNear - z * (zFar - zNear));  
}

in vec2 TexCoord;
void main()
{ 
    float depthValue = texture(depthMap, TexCoord).r;
    //float depth = LinearizeDepth(gl_FragCoord.z) / far; // only for perspective 
    FragColor = vec4(vec3(depthValue), 1.0);
}

Answer 1

_lightSpaceMatrix的计算错误。 OpenTK 矩阵乘法是相反的。见 Problem with matrices #687:

Because of how matrices are treated in C# and OpenTK, multiplication order is inverted from what you might expect in C/C++ and GLSL. This is an old artefact in the library, and it's too late to change now, unfortunately.

矩阵相乘时交换_ligthView和_lightProjection：

~~_lightSpaceMatrix = _lightProjection * _ligthView;~~

_lightSpaceMatrix = _ligthView * _lightProjection;

Opengl OpenTK - 绘制深度缓冲区时出现白屏

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