[英]Why is my triangle white in OpenGL ES 3 on Raspberry Pi
我有一個非常簡單的 OpenGL ES 程序示例,我試圖在 Raspberry Pi 4 上的 RaspiOS Desktop(又名 Raspbian)上運行該程序。
我的目標很簡單——在屏幕中央畫一個紅色三角形。 但是,三角形顯示為白色而不是紅色。
我已經搜索並嘗試了所有方法,但找不到任何幫助。 在這一點上我感到非常沮喪,因為這應該是第一個介紹 OpenGL ES 世界的教程,而我已經陷入困境,無法繼續更復雜的示例。
無論如何,這是完整的例子
#include <GL/glew.h>
#include <GL/freeglut.h>
#include <stdio.h>
#include <stdbool.h>
static struct glData {
GLuint program;
GLuint vbo;
} glData;
const char vert_shader_source[] = "#version 300 es \n"
"precision mediump float; \n"
"layout (location = 0) in vec3 Position; \n"
"void main() \n"
"{ \n"
" gl_Position = vec4(Position, 1.0); \n"
"} \n";
const char frag_shader_source[] = "#version 300 es \n"
"precision mediump float; \n"
"out vec4 fragColor; \n"
"void main() \n"
"{ \n"
" fragColor = vec4(1.0f, 0.0f, 0.0f, 1.0f); \n"
"} \n";
#define POSITION 0
bool initWindow(int* argc, char** argv)
{
glutInit(argc, argv);
glutInitDisplayMode(GLUT_DOUBLE | GLUT_RGB | GLUT_MULTISAMPLE);
glutCreateWindow("Triangle");
GLenum glew_status = glewInit();
if (glew_status != GLEW_OK) {
fprintf(stderr, "Error: %s\n", glewGetErrorString(glew_status));
return false;
}
return true;
}
static GLuint buildShader(const char* shader_source, GLenum type)
{
GLuint shader;
GLint status;
shader = glCreateShader(type);
if (shader == 0) {
return 0;
}
glShaderSource(shader, 1, &shader_source, NULL);
glCompileShader(shader);
glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
if (status != GL_TRUE) {
int length;
char* log;
fprintf(stderr, "failed to compile shader\n");
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &length);
if (length > 1) {
log = calloc(length, sizeof(char));
glGetShaderInfoLog(shader, length, &length, log);
fprintf(stderr, "%s\n", log);
free(log);
}
return false;
}
return true;
}
static GLuint createAndLinkProgram(GLuint v_shader, GLuint f_shader)
{
GLuint program;
GLint linked;
program = glCreateProgram();
if (program == 0) {
fprintf(stderr, "failed to create program\n");
return 0;
}
glAttachShader(program, v_shader);
glAttachShader(program, f_shader);
glLinkProgram(program);
glGetProgramiv(program, GL_LINK_STATUS, &linked);
if (linked != GL_TRUE) {
int length;
char* log;
fprintf(stderr, "failed to link program\n");
glGetProgramiv(program, GL_INFO_LOG_LENGTH, &length);
if (length > 1) {
log = calloc(length, sizeof(char));
glGetProgramInfoLog(program, length, &length, log);
fprintf(stderr, "%s\n", log);
free(log);
}
glDeleteProgram(program);
return 0;
}
return program;
}
static bool initProgram()
{
GLuint v_shader, f_shader;
v_shader = buildShader(vert_shader_source, GL_VERTEX_SHADER);
if (v_shader == 0) {
fprintf(stderr, "failed to build vertex shader\n");
return false;
}
f_shader = buildShader(frag_shader_source, GL_FRAGMENT_SHADER);
if (f_shader == 0) {
fprintf(stderr, "failed to build fragment shader\n");
glDeleteShader(v_shader);
return false;
}
glReleaseShaderCompiler(); // should release resources allocated for the compiler
glData.program = createAndLinkProgram(v_shader, f_shader);
if (glData.program == 0) {
fprintf(stderr, "failed to create and link program\n");
glDeleteShader(v_shader);
glDeleteShader(f_shader);
return false;
}
glUseProgram(glData.program);
// this won't actually delete the shaders until the program is closed but it's a good practice
glDeleteShader(v_shader);
glDeleteShader(f_shader);
return true;
}
bool setupOpenGL()
{
if (!initProgram()) {
fprintf(stderr, "failed to initialize program\n");
return false;
}
GLfloat vVertices[] = {
-0.5f, -0.5f, 0.0f,
0.0f, 0.5f, 0.0f,
0.5f, -0.5f, 0.0f,
};
glClearColor(0, 0, 0, 1);
glGenBuffers(1, &glData.vbo);
glBindBuffer(GL_ARRAY_BUFFER, glData.vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vVertices), vVertices, GL_STATIC_DRAW);
return true;
}
void reshape(int width, int height)
{
glViewport(0, 0, width, height);
}
void drawTriangle()
{
glClear(GL_COLOR_BUFFER_BIT);
glEnableVertexAttribArray(POSITION);
glBindBuffer(GL_ARRAY_BUFFER, glData.vbo);
glVertexAttribPointer(POSITION, 3, GL_FLOAT, GL_FALSE, 0, 0);
glDrawArrays(GL_TRIANGLES, 0, 3);
glDisableVertexAttribArray(POSITION);
glutSwapBuffers();
}
int main(int argc, char** argv)
{
printf("initialize window\n");
if (!initWindow(&argc, argv)) {
fprintf(stderr, "failed to initialize window\n");
return EXIT_FAILURE;
}
printf("setup opengl\n");
if (!setupOpenGL()) {
fprintf(stderr, "failed to setup opengl\n");
return EXIT_FAILURE;
}
glutDisplayFunc(drawTriangle);
glutReshapeFunc(reshape);
glutMainLoop();
glDeleteProgram(glData.program);
return EXIT_SUCCESS;
}
在運行它之前,您需要:
sudo raspi-config
然后你可以像這樣編譯和運行它:
gcc triangle.c -Wall -lm -lglut -lGLEW -lGL -o triangle
./triangle
起初我以為可能是驅動程序中的一些錯誤或其他東西。 但是后來我找到了這個例子並嘗試運行它,它繪制了一些帶有多個 colors 的圖形,這很好。
我會很感激任何幫助。 這幾天我一直在嘗試調試它。
Nvm,原來我是個白痴。
這一直是buildShader()
function 中的一個簡單錯字。 這是 function 的固定版本:
static GLuint buildShader(const char* shader_source, GLenum type)
{
GLuint shader;
GLint status;
shader = glCreateShader(type);
if (shader == 0) {
return 0;
}
glShaderSource(shader, 1, &shader_source, NULL);
glCompileShader(shader);
glGetShaderiv(shader, GL_COMPILE_STATUS, &status);
if (status != GL_TRUE) {
int length;
char* log;
fprintf(stderr, "failed to compile shader\n");
glGetShaderiv(shader, GL_INFO_LOG_LENGTH, &length);
if (length > 1) {
log = calloc(length, sizeof(char));
glGetShaderInfoLog(shader, length, &length, log);
fprintf(stderr, "%s\n", log);
free(log);
}
return 0;
}
return shader;
}
問題是我不小心返回了真/假而不是着色器。 我完全不知道該程序如何仍然成功運行而沒有錯誤並顯示一個白色三角形,但事實就是如此。
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