Add multisampled FBO support

src/k3.c

@@ -2744,14 +2744,29 @@ struct k3ARBFP *k3ProgramARBFP(const char *src) {
 	return (struct k3ARBFP*) (uintptr_t) p;
 }
 
-struct k3Offscreen *k3OffscreenCreate(struct k3Tex *diffuse, struct k3Tex *depth) {
+struct k3Offscreen *k3OffscreenCreateMultisampled(struct k3Tex *diffuse, struct k3Tex *depth, uint8_t samples) {
 	k3Log(k3_INFO, "Init %sFBO", !diffuse && depth ? "depth-only " : "");
 	
+	if(samples && (!GLAD_GL_EXT_framebuffer_multisample || !GLAD_GL_EXT_framebuffer_blit)) {
+		samples = 0;
+		k3Log(k3_WARN, "Multisampled offscreens not supported.");
+	}
+	
+	if(!GLAD_GL_EXT_framebuffer_object) {
+		k3Log(k3_ERR, "Non-FBO offscreens not implemented");
+		return NULL;
+	}
+	
 	GLuint fbo = 0;
-	if(GLAD_GL_EXT_framebuffer_object) {
 	glGenFramebuffersEXT(1, &fbo);
 	glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
 	
+	struct k3Offscreen *ret = calloc(1, sizeof(*ret));
+	ret->fbo = fbo;
+	ret->diffuse = diffuse;
+	ret->depth = depth;
+	ret->multisampling.samples = samples;
+	
 	if(diffuse) {
 		glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_TEXTURE_2D, GL_FROM_K3TEX(diffuse), 0);
 	} else {
@@ -2767,23 +2782,43 @@ struct k3Offscreen *k3OffscreenCreate(struct k3Tex *diffuse, struct k3Tex *depth
 		k3Log(k3_WARN, "Framebuffer incomplete");
 	}
 	
-		glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
+	if(samples) {
-		glDrawBuffer(GL_BACK); // XXX: this should not be necessary
+		GLuint msfbo;
-	} else {
+		glGenFramebuffersEXT(1, &msfbo);
-		k3Log(k3_ERR, "Non-FBO offscreens not implemented");
+		glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, msfbo);
-		return NULL;
+		
+		ret->multisampling.fbo = msfbo;
+		
+		if(diffuse) {
+			glGenRenderbuffersEXT(1, &ret->multisampling.rboDiffuse);
+			glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, ret->multisampling.rboDiffuse);
+			glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER_EXT, samples, diffuse->glInternalFormat, diffuse->szX, diffuse->szY);
+			glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_COLOR_ATTACHMENT0_EXT, GL_RENDERBUFFER_EXT, ret->multisampling.rboDiffuse);
 		}
 		
-	struct k3Offscreen *ret = malloc(sizeof(*ret));
+		if(depth) {
-	ret->fbo = fbo;
+			glGenRenderbuffersEXT(1, &ret->multisampling.rboDepth);
-	ret->diffuse = diffuse;
+			glBindRenderbufferEXT(GL_RENDERBUFFER_EXT, ret->multisampling.rboDepth);
-	ret->depth = depth;
+			glRenderbufferStorageMultisampleEXT(GL_RENDERBUFFER_EXT, samples, depth->glInternalFormat, depth->szX, depth->szY);
+			glFramebufferRenderbufferEXT(GL_FRAMEBUFFER_EXT, GL_DEPTH_ATTACHMENT_EXT, GL_RENDERBUFFER_EXT, ret->multisampling.rboDepth);
+		}
+	}
+	
+	glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
+	glDrawBuffer(GL_BACK); // XXX: this should not be necessary
+	
 	return ret;
 }
 
+struct k3Offscreen *k3OffscreenCreate(struct k3Tex *diffuse, struct k3Tex *depth) {
+	return k3OffscreenCreateMultisampled(diffuse, depth, 0);
+}
+
 void k3BeginOffscreen(struct k3Offscreen *offscr) {
 	if(GLAD_GL_EXT_framebuffer_object) {
-		glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, offscr->fbo);
+		GLuint fbo = offscr->multisampling.samples > 0 ? offscr->multisampling.fbo : offscr->fbo;
+		
+		glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo);
 		
 		struct k3Tex *t = offscr->diffuse ? offscr->diffuse : offscr->depth;
 		glViewport(0, 0, k3TexSzX(t), k3TexSzY(t));
@@ -2794,6 +2829,12 @@ void k3BeginOffscreen(struct k3Offscreen *offscr) {
 
 void k3EndOffscreen(struct k3Offscreen *offscr) {
 	if(GLAD_GL_EXT_framebuffer_object) {
+		if(offscr->multisampling.samples) {
+			glBindFramebufferEXT(GL_DRAW_FRAMEBUFFER_EXT, offscr->fbo);
+			
+			glBlitFramebufferEXT(0, 0, offscr->diffuse->szX, offscr->diffuse->szY, 0, 0, offscr->diffuse->szX, offscr->diffuse->szY, GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT, GL_NEAREST);
+		}
+		
 		glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, 0);
 		glViewport(0, 0, MainWidth, MainHeight);
 	} else {
@@ -2809,7 +2850,9 @@ void k3BlitToScreenEffect(struct k3Offscreen *offscr, int additive, int effect,
 	if(GLAD_GL_EXT_framebuffer_object) {
 		glActiveTexture(GL_TEXTURE0);
 		
-		glBindTexture(GL_TEXTURE_2D, GL_FROM_K3TEX(offscr->diffuse));
+		struct k3Tex *tex = offscr->diffuse ? offscr->diffuse : offscr->depth;
+		
+		glBindTexture(GL_TEXTURE_2D, GL_FROM_K3TEX(tex));
 		
 		if(additive) {
 			glEnable(GL_BLEND);
@@ -2856,7 +2899,7 @@ void k3BlitToScreenEffect(struct k3Offscreen *offscr, int additive, int effect,
 			}
 			
 			GLint uSz = glGetUniformLocation(GL_FROM_K3GLSL(basicBlitProgram), "u_sz");
-			glUniform2f(uSz, k3TexSzX(offscr->diffuse), k3TexSzY(offscr->diffuse));
+			glUniform2f(uSz, k3TexSzX(tex), k3TexSzY(tex));
 			
 			glDrawArrays(GL_TRIANGLES, 0, 3);
 		} else {
@@ -2864,8 +2907,8 @@ void k3BlitToScreenEffect(struct k3Offscreen *offscr, int additive, int effect,
 				glUseProgramObjectARB(effect == k3_GLSL ? GL_FROM_K3GLSL(program) : 0);
 			}
 			
-			float bleedW = 1.0f / k3TexSzX(offscr->diffuse);
+			float bleedW = 1.0f / k3TexSzX(tex);
-			float bleedH = 1.0f / k3TexSzY(offscr->diffuse);
+			float bleedH = 1.0f / k3TexSzY(tex);
 			
 			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 			glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);

src/k3.h

@@ -190,6 +190,7 @@ void k3PassDepthOnly(mat4 projection, mat4 cam, int clear, int cull);
 void k3PassShadowmap(mat4 projection, mat4 cam, struct k3Offscreen *offscr);
 
 struct k3Offscreen;
+struct k3Offscreen *k3OffscreenCreateMultisampled(struct k3Tex *diffuse, struct k3Tex *depth, uint8_t samples);
 struct k3Offscreen *k3OffscreenCreate(struct k3Tex *diffuse, struct k3Tex *depth);
 void k3BeginOffscreen(struct k3Offscreen*);
 void k3EndOffscreen(struct k3Offscreen*);

src/k3_internal.h

@@ -45,6 +45,13 @@ struct k3Offscreen {
 	GLuint fbo;
 	struct k3Tex *diffuse;
 	struct k3Tex *depth;
+	
+	struct {
+		uint8_t samples;
+		GLuint fbo;
+		GLuint rboDiffuse;
+		GLuint rboDepth;
+	} multisampling;
 };
 
 struct k3Mdl {