glpointsize() 缩小一个点失败
glpointsize() Fails to Shrink a Point
我正在尝试编写一个简单的 opengl 程序,该程序使用 glPointSize()
和变量 pointSize
循环增大和缩小屏幕中心的单个点。打印 pointSize
的值并使用调试器单步执行代码似乎表明 pointSize
在每次迭代时正确更新。当 pointSize
增加时,该点的渲染似乎也是正确的,但是当 pointSize
减少时,该点仍以其最大尺寸呈现在屏幕上,并且无论多大都保持这种方式呈现pointSize
价值增加或减少 - 我不明白为什么。
#include <GL\glew.h>
#include <GLFW\glfw3.h>
#include <iostream>
#define numVAOs 1
GLuint renderingProgram;
GLuint vao[numVAOs];
GLuint createShaderProgram() {
const char *vshaderSource =
"#version 430 \n"
"void main(void) \n"
"{ gl_Position = vec4(0.0, 0.0, 0.0, 1.0); }";
const char *fshaderSource =
"#version 430 \n"
"out vec4 color; \n"
"void main(void) \n"
"{ color = vec4(0.0, 0.0, 1.0, 1.0); }";
GLuint vShader = glCreateShader(GL_VERTEX_SHADER);
GLuint fShader = glCreateShader(GL_FRAGMENT_SHADER);
GLuint vfprogram = glCreateProgram();
glShaderSource(vShader, 1, &vshaderSource, NULL);
glShaderSource(fShader, 1, &fshaderSource, NULL);
glCompileShader(vShader);
glCompileShader(fShader);
glAttachShader(vfprogram, vShader);
glAttachShader(vfprogram, fShader);
glLinkProgram(vfprogram);
return vfprogram;
}
void init() {
renderingProgram = createShaderProgram();
glGenVertexArrays(numVAOs, vao);
glBindVertexArray(vao[0]);
}
GLfloat pointSize = 100.0f;
GLfloat increment = 1.0f;
void display() {
glUseProgram(renderingProgram);
if (pointSize > 200 || pointSize < 2) increment *= -1.0f;
pointSize += increment;
glPointSize(pointSize);
glDrawArrays(GL_POINTS, 0, 1);
}
int main(void) {
if (!glfwInit()) exit(EXIT_FAILURE);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
GLFWwindow* window = glfwCreateWindow(600, 600, "Test", nullptr, nullptr);
glfwMakeContextCurrent(window);
if (glewInit() != GLEW_OK) exit(EXIT_FAILURE);
glfwSwapInterval(1);
init();
while (!glfwWindowShouldClose(window)) {
display();
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwDestroyWindow(window);
glfwTerminate();
exit(EXIT_SUCCESS);
}
您的代码没有使用 glClear
清除屏幕。因此,当点增长时,您可以看到它。当它缩小时,它只是绘制 'inside' 更大的点,而您没有注意到它。如果在点的大小发生变化时更改点的颜色,您可能会注意到这一点。
只需清除帧开头的颜色缓冲区:
void display() {
// default clear color is black, but you can change it:
//glClearColor(1,0,0,1);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(renderingProgram);
...
我正在尝试编写一个简单的 opengl 程序,该程序使用 glPointSize()
和变量 pointSize
循环增大和缩小屏幕中心的单个点。打印 pointSize
的值并使用调试器单步执行代码似乎表明 pointSize
在每次迭代时正确更新。当 pointSize
增加时,该点的渲染似乎也是正确的,但是当 pointSize
减少时,该点仍以其最大尺寸呈现在屏幕上,并且无论多大都保持这种方式呈现pointSize
价值增加或减少 - 我不明白为什么。
#include <GL\glew.h>
#include <GLFW\glfw3.h>
#include <iostream>
#define numVAOs 1
GLuint renderingProgram;
GLuint vao[numVAOs];
GLuint createShaderProgram() {
const char *vshaderSource =
"#version 430 \n"
"void main(void) \n"
"{ gl_Position = vec4(0.0, 0.0, 0.0, 1.0); }";
const char *fshaderSource =
"#version 430 \n"
"out vec4 color; \n"
"void main(void) \n"
"{ color = vec4(0.0, 0.0, 1.0, 1.0); }";
GLuint vShader = glCreateShader(GL_VERTEX_SHADER);
GLuint fShader = glCreateShader(GL_FRAGMENT_SHADER);
GLuint vfprogram = glCreateProgram();
glShaderSource(vShader, 1, &vshaderSource, NULL);
glShaderSource(fShader, 1, &fshaderSource, NULL);
glCompileShader(vShader);
glCompileShader(fShader);
glAttachShader(vfprogram, vShader);
glAttachShader(vfprogram, fShader);
glLinkProgram(vfprogram);
return vfprogram;
}
void init() {
renderingProgram = createShaderProgram();
glGenVertexArrays(numVAOs, vao);
glBindVertexArray(vao[0]);
}
GLfloat pointSize = 100.0f;
GLfloat increment = 1.0f;
void display() {
glUseProgram(renderingProgram);
if (pointSize > 200 || pointSize < 2) increment *= -1.0f;
pointSize += increment;
glPointSize(pointSize);
glDrawArrays(GL_POINTS, 0, 1);
}
int main(void) {
if (!glfwInit()) exit(EXIT_FAILURE);
glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 4);
glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
GLFWwindow* window = glfwCreateWindow(600, 600, "Test", nullptr, nullptr);
glfwMakeContextCurrent(window);
if (glewInit() != GLEW_OK) exit(EXIT_FAILURE);
glfwSwapInterval(1);
init();
while (!glfwWindowShouldClose(window)) {
display();
glfwSwapBuffers(window);
glfwPollEvents();
}
glfwDestroyWindow(window);
glfwTerminate();
exit(EXIT_SUCCESS);
}
您的代码没有使用 glClear
清除屏幕。因此,当点增长时,您可以看到它。当它缩小时,它只是绘制 'inside' 更大的点,而您没有注意到它。如果在点的大小发生变化时更改点的颜色,您可能会注意到这一点。
只需清除帧开头的颜色缓冲区:
void display() {
// default clear color is black, but you can change it:
//glClearColor(1,0,0,1);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(renderingProgram);
...