Unplug SDL_Renderer from OpenGL process. Use FrameBufferObject.

3 files changed, 53 insertions, 12 deletions

diff --git a/src/demoscene-eo.c b/src/demoscene-eo.c
index 94db4e5..ed6fe1b 100644
--- a/src/demoscene-eo.c
+++ b/src/demoscene-eo.c
@@ -367,7 +367,7 @@ int worker_gl() {
 	SDL_GL_SetAttribute(SDL_GL_BLUE_SIZE, 8);
 	SDL_GL_SetAttribute(SDL_GL_ALPHA_SIZE, 8);
 	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
-	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
+	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 3);
 	SDL_GL_SetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, SDL_GL_CONTEXT_PROFILE_CORE);
 
 	// Initialize OpenGL
diff --git a/src/main.h b/src/main.h
index bf622ed..a8e0722 100644
--- a/src/main.h
+++ b/src/main.h
@@ -36,7 +36,8 @@ typedef struct {
 	// OpenGL worker
 	SDL_Window* gl_win;
 	SDL_GLContext gl_ctx;
-	SDL_Renderer *gl_rndr;
+	SDL_Renderer *gl_rndr; //XXX remove me
+	GLuint gl_fbo;
 	SDL_Texture *gl_target;
 	// framebuffer to inject OpenGL or SDL result in caca canvas
 	uint32_t raw_target[FBUF_W*FBUF_H];
diff --git a/src/scene01.c b/src/scene01.c
index 39083d0..a93aa3d 100644
--- a/src/scene01.c
+++ b/src/scene01.c
@@ -75,7 +75,9 @@ typedef enum t_attrib_id
 } t_attrib_id;
 
 int scene01_init_gl(graphical_env_t *ge, scene01_env_t *se) {
-	GLuint vs, fs, program;
+	GLuint vs, fs, program, vbo, renderedTexture, depthrenderbuffer;
+	GLint status;
+	GLenum DrawBuffers[1] = {GL_COLOR_ATTACHMENT0};
 
 	TRACE("call");
 	vs = glCreateShader(GL_VERTEX_SHADER);
@@ -85,7 +87,6 @@ int scene01_init_gl(graphical_env_t *ge, scene01_env_t *se) {
 	glShaderSource(vs, 1, (const GLchar **)&vertex_shader, &length);
 	glCompileShader(vs);
 
-	GLint status;
 	glGetShaderiv(vs, GL_COMPILE_STATUS, &status);
 	if(status == GL_FALSE) return 40;
 
@@ -106,12 +107,45 @@ int scene01_init_gl(graphical_env_t *ge, scene01_env_t *se) {
 
 	glUseProgram(program);
 
+	// http://www.opengl-tutorial.org/intermediate-tutorials/tutorial-14-render-to-texture/
+
+	// The framebuffer, which regroups 0, 1, or more textures, and 0 or 1 depth buffer.
+	glGenFramebuffers(1, &ge->gl_fbo);
+
+	// The texture we're going to render to
+	glGenTextures(1, &renderedTexture);
+
+	// "Bind" the newly created texture : all future texture functions will modify this texture
+	glBindTexture(GL_TEXTURE_2D, renderedTexture);
+
+	// Give an empty image to OpenGL ( the last "0" )
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, FBUF_W, FBUF_H, 0, GL_RGB, GL_UNSIGNED_BYTE, 0);
+
+	// Poor filtering. Needed !
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
+	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
+
+	// The depth buffer
+	glGenRenderbuffers(1, &depthrenderbuffer);
+	glBindRenderbuffer(GL_RENDERBUFFER, depthrenderbuffer);
+	glRenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT, FBUF_W, FBUF_H);
+	glFramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, depthrenderbuffer);
+
+	// Set "renderedTexture" as our colour attachement #0
+	glFramebufferTexture(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, renderedTexture, 0);
+
+	// Set the list of draw buffers.
+	glDrawBuffers(1, DrawBuffers); // "1" is the size of DrawBuffers
+
+	// Always check that our framebuffer is ok
+	if(glCheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE) {
+		return 1;
+	}
+
 	glDisable(GL_DEPTH_TEST);
-	glClearColor(0.5, 0.0, 0.0, 0.0);
+	//glClearColor(0.5, 0.0, 0.0, 0.0);
 	glViewport(0, 0, FBUF_W, FBUF_H);
 
-	GLuint vbo;
-
 	glGenVertexArrays(1, &(se->vao));
 	glGenBuffers(1, &vbo);
 	glBindVertexArray(se->vao);
@@ -139,6 +173,8 @@ int scene01_init_gl(graphical_env_t *ge, scene01_env_t *se) {
 	t_mat4x4 projection_matrix;
 	mat4x4_ortho(projection_matrix, 0.0f, (float)FBUF_W, (float)FBUF_H, 0.0f, 0.0f, 100.0f);
 	glUniformMatrix4fv(glGetUniformLocation(program, "u_projection_matrix"), 1, GL_FALSE, projection_matrix);
+
+
 	return 0;
 }
 
@@ -166,21 +202,25 @@ void scene01_free_caca(graphical_env_t *ge, scene01_env_t *se) {
 }
 
 int scene01_next_gl(graphical_env_t *ge, scene01_env_t *se) {
-	SDL_Renderer *r = ge->gl_rndr;
 	TRACE_CALL_ONCE;
 
-	// https://gist.github.com/Twinklebear/8265888
-	// https://forums.libsdl.org/viewtopic.php?p=51634
+	// Render to the in-VRAM Framebuffer Object
+	glBindFramebuffer(GL_FRAMEBUFFER, ge->gl_fbo);
 
 	glClear(GL_COLOR_BUFFER_BIT);
 	glBindVertexArray(se->vao);
 	glDrawArrays(GL_TRIANGLES, 0, 6);
 	// [...]
 
-	//SDL_GL_SwapWindow(ge->gl_win);
+	// Render to the screen
+	glBindFramebuffer(GL_FRAMEBUFFER, 0);
+	glClear(GL_COLOR_BUFFER_BIT);
+	glBindVertexArray(se->vao);
+	glDrawArrays(GL_TRIANGLES, 0, 6);
+	SDL_GL_SwapWindow(ge->gl_win);
 	
 	// Download the rendered texture from videocard to main memory
-	SDL_RenderReadPixels(r, NULL, 0, ge->raw_target, FBUF_W*4);
+	//SDL_RenderReadPixels(r, NULL, 0, ge->raw_target, FBUF_W*4);
 
 	return 0;
 }