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Add a framebuffer to hold a texture

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This commit is contained in:
Dimitri Lozeve 2021-02-24 21:48:54 +01:00
parent 57cdfca13d
commit 60d94b06f2
4 changed files with 130 additions and 33 deletions
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15
shaders/invert_screen.frag Normal file
View file

@ -0,0 +1,15 @@
#version 330 core
out vec4 FragColor;
in vec2 TexCoords;
uniform float u_time;
uniform uint u_frame;
uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform sampler2D u_texture;
void main() {
//FragColor = texture(u_texture, TexCoords);
FragColor = vec4(1.0 - texelFetch(u_texture, ivec2(gl_FragCoord), 0));
}

125
src/main.c
View file

@ -11,10 +11,16 @@
int main(int argc, char *argv[]) {
if (argc < 2) {
log_error("Usage: %s <fragment shader>", argv[0]);
log_error("Usage: %s <screen shader> [<buffer shader>]", argv[0]);
return EXIT_FAILURE;
}
const char *fragment_shader_file = argv[1];
const char *screen_shader_file = argv[1];
log_debug("Screen shader file: %s", screen_shader_file);
const char *buffer_shader_file = NULL;
if (argc >= 3) {
buffer_shader_file = argv[2];
log_debug("Buffer shader file: %s", buffer_shader_file);
}
GLFWwindow *window = initialize_window(WINDOW_WIDTH, WINDOW_HEIGHT);
if (window == NULL) {
@ -24,45 +30,110 @@ int main(int argc, char *argv[]) {
unsigned int VAO = initialize_vertices();
unsigned int shader_program = glCreateProgram();
if (!shader_program) {
log_error("Could not create shader program");
unsigned int screen_shader = glCreateProgram();
if (!screen_shader) {
log_error("Could not create screen shader program");
glfwDestroyWindow(window);
glfwTerminate();
return EXIT_FAILURE;
}
compile_shaders(&shader_program, fragment_shader_file);
compile_shaders(&screen_shader, screen_shader_file);
unsigned int buffer_shader = 0;
unsigned int framebuffer = 0;
if (buffer_shader_file) {
buffer_shader = glCreateProgram();
if (!buffer_shader) {
log_error("Could not create buffer shader program");
glfwDestroyWindow(window);
glfwTerminate();
return EXIT_FAILURE;
}
compile_shaders(&buffer_shader, buffer_shader_file);
/* Framebuffer */
framebuffer = 0;
glGenFramebuffers(1, &framebuffer);
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
/* color attachment texture */
unsigned int texture_color_buffer = 0;
glGenTextures(1, &texture_color_buffer);
glBindTexture(GL_TEXTURE_2D, texture_color_buffer);
glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, WINDOW_WIDTH, WINDOW_HEIGHT, 0,
GL_RGB, GL_UNSIGNED_BYTE, NULL);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D,
texture_color_buffer, 0);
/* check that the framebuffer is complete */
if (glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
log_error("Framebuffer is not complete");
} else {
log_debug("Framebuffer initialized and complete");
}
glBindFramebuffer(GL_FRAMEBUFFER, 0);
}
/* Drawing loop */
size_t frame = 0;
while (!glfwWindowShouldClose(window)) {
process_input(window, &shader_program, fragment_shader_file);
process_input(window, &screen_shader, screen_shader_file, &buffer_shader,
buffer_shader_file);
/* Background */
glClearColor(0, 0, 0, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(shader_program);
/* Setup uniforms */
/* data required for uniforms */
float time = glfwGetTime();
int frag_time_location = glGetUniformLocation(shader_program, "u_time");
glUniform1f(frag_time_location, time);
int frag_frame_location = glGetUniformLocation(shader_program, "u_frame");
glUniform1ui(frag_frame_location, frame);
int viewport[4] = {0};
glGetIntegerv(GL_VIEWPORT, viewport);
int frag_resolution_location =
glGetUniformLocation(shader_program, "u_resolution");
glUniform2f(frag_resolution_location, viewport[2], viewport[3]);
double mouse_x = 0, mouse_y = 0;
glfwGetCursorPos(window, &mouse_x, &mouse_y);
int frag_mouse_resolution_location =
glGetUniformLocation(shader_program, "u_mouse");
glUniform2f(frag_mouse_resolution_location, mouse_x, mouse_y);
if (frame % 100 == 0) {
log_debug("frame = %zu, time = %f, viewport = (%d, %d)", frame, time,
viewport[2], viewport[3]);
}
if (buffer_shader_file) {
/* bind the framebuffer and draw to it */
glBindFramebuffer(GL_FRAMEBUFFER, framebuffer);
/* Background */
glClearColor(0, 0, 0, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(buffer_shader);
/* Setup uniforms */
glUniform1ui(glGetUniformLocation(buffer_shader, "u_frame"), frame);
glUniform1f(glGetUniformLocation(buffer_shader, "u_time"), time);
glUniform2f(glGetUniformLocation(buffer_shader, "u_resolution"),
viewport[2], viewport[3]);
glUniform2f(glGetUniformLocation(buffer_shader, "u_mouse"), mouse_x,
mouse_y);
glUniform1d(glGetUniformLocation(buffer_shader, "u_texture"), 0);
/* Draw the vertices */
// glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); /* For wireframe mode */
glBindVertexArray(VAO);
glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
glBindVertexArray(0);
/* bind back to default framebuffer */
glBindFramebuffer(GL_FRAMEBUFFER, 0);
}
glClearColor(1.0, 1.0, 1.0, 1.0);
glClear(GL_COLOR_BUFFER_BIT);
glUseProgram(screen_shader);
/* Setup uniforms */
glUniform1ui(glGetUniformLocation(screen_shader, "u_frame"), frame);
glUniform1f(glGetUniformLocation(screen_shader, "u_time"), time);
glUniform2f(glGetUniformLocation(screen_shader, "u_resolution"),
viewport[2], viewport[3]);
glUniform2f(glGetUniformLocation(screen_shader, "u_mouse"), mouse_x,
mouse_y);
glUniform1d(glGetUniformLocation(screen_shader, "u_texture"), 0);
/* Draw the vertices */
// glPolygonMode(GL_FRONT_AND_BACK, GL_LINE); /* For wireframe mode */

19
src/renderer.c
View file

@ -62,13 +62,14 @@ GLFWwindow *initialize_window(int width, int height) {
unsigned int initialize_vertices() {
/* Define vertices */
float vertices[] = {
-1.0, -1.0, 0.0, // bottom left
-1.0, 1.0, 0.0, // top left
1.0, -1.0, 0.0, // top right
1.0, 1.0, 0.0 // bottom right
// positions // texture coords
1.0, 1.0, 0.0, 1.0, 1.0, // top right
1.0, -1.0, 0.0, 1.0, 0.0, // bottom right
-1.0, -1.0, 0.0, 0.0, 0.0, // bottom left
-1.0, 1.0, 0.0, 0.0, 1.0, // top left
};
unsigned int indices[] = {
0, 1, 2, // first triangle
0, 1, 3, // first triangle
1, 2, 3 // second triangle
};
@ -86,8 +87,14 @@ unsigned int initialize_vertices() {
glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices,
GL_STATIC_DRAW);
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void *)0);
/* position attribute */
glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float), (void *)0);
glEnableVertexAttribArray(0);
/* texture coord attribute */
glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 5 * sizeof(float),
(void *)(3 * sizeof(float)));
glEnableVertexAttribArray(1);
log_debug("Vertex data initialized successfully");
return VAO;

4
src/shaders.c
View file

@ -63,13 +63,17 @@ char *read_file(const char *const filename) {
*/
int compile_shaders(unsigned int *shader_program,
const char *const fragment_shader_file) {
log_debug("Compiling %s", fragment_shader_file);
/* Compile vertex shader */
const char *const vertex_shader_source =
"#version 330 core\n"
"layout (location = 0) in vec3 aPos;\n"
"layout (location = 1) in vec2 aTexCoord;\n"
"out vec2 TexCoord;\n"
"void main()\n"
"{\n"
" gl_Position = vec4(aPos, 1.0);\n"
" TexCoord = aTexCoord;\n"
"}\n";
unsigned int vertex_shader = glCreateShader(GL_VERTEX_SHADER);