From f850e3f08278a5e1d50045d25e519708cb486e08 Mon Sep 17 00:00:00 2001
From: bx <bx@tilde.town>
Date: Mon, 21 Mar 2022 21:56:24 +0000
Subject: [PATCH] got uniform iResolution working

---
 sdfps.c | 63 ++++++++++++++++++++++++++++++++++++++-------------------
 1 file changed, 42 insertions(+), 21 deletions(-)

diff --git a/sdfps.c b/sdfps.c
index 5a288dc..e853fb4 100644
--- a/sdfps.c
+++ b/sdfps.c
@@ -4,6 +4,8 @@
 
 #include <glad/glad.h>
 
+#include <stdio.h>
+
 #include "types.h"
 
 GLuint create_shader(GLenum shader_type, const char *src) {
@@ -54,10 +56,15 @@ void init(Sdfps* s) { /* TODO: Error checks */
 	s -> frag_shader = create_shader(GL_FRAGMENT_SHADER,
 		"#version 330\n"
 		"precision highp float;\n"
+
+		/* viewport resolution (in pixels), z = 1 */
+		"uniform vec3 iResolution;\n"
+
 		"out vec4 out_color;\n"
 		"void main() {\n"
-			"vec2 xy = mod(gl_FragCoord.xy, vec2(200.0, 200.0));\n"
-			"out_color = vec4(xy.x / 100.0, xy.x / 200.0, xy.y / 200.0, 1);\n"
+			"vec2 xy = gl_FragCoord.xy;\n"
+			"out_color = vec4(sin(xy.x), sin(xy.y), sin(xy.x) + sin(xy.y), 1);\n"
+			"if(xy.x > iResolution.x / 2.0) out_color = out_color.zxyw;\n"
 		"}\n");
 
 	s -> shader_program = glCreateProgram();
@@ -75,34 +82,44 @@ void init(Sdfps* s) { /* TODO: Error checks */
 }
 
 void deinit(Sdfps *s) {
+	glDeleteProgram(s -> shader_program);
+	glDeleteShader(s -> vert_shader);
+	glDeleteShader(s -> frag_shader);
 	SDL_GL_DeleteContext(s -> context);
 	SDL_DestroyWindow(s -> window);
 }
 
-void render(Sdfps *s) {
-	// setup render texture
-	const s32 fb_w = 512, fb_h = 512;
-	GLuint render_tex;
-	glGenTextures(1, &render_tex);
-	glBindTexture(GL_TEXTURE_2D, render_tex);
+s32 create_framebuffer(s32 w, s32 h, GLuint *texture, GLuint *framebuffer) {
+	glGenTextures(1, texture);
+	glBindTexture(GL_TEXTURE_2D, *texture);
 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR);
 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
 	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
-	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA,
-		fb_w, fb_h, // width height
-		0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
-	GLuint framebuf;
-	glGenFramebuffers(1, &framebuf);
-	glBindFramebuffer(GL_FRAMEBUFFER, framebuf);
-	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, render_tex, 0);
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGBA, w, h, 0, GL_RGBA, GL_UNSIGNED_BYTE, NULL);
+
+	glGenFramebuffers(1, framebuffer);
+	glBindFramebuffer(GL_FRAMEBUFFER, *framebuffer);
+	glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, *texture, 0);
+
 	GLenum fb_status = glCheckFramebufferStatus(GL_FRAMEBUFFER);
-	if (fb_status != GL_FRAMEBUFFER_COMPLETE)
+	if (fb_status != GL_FRAMEBUFFER_COMPLETE) {
 		puts("FRAME BUFFER FUCKED UP SOMEWHERE");
+		return 1;
+	}
+	return 0;
+}
+
+void render(Sdfps *s) {
+	// setup render texture
+	const s32 fb_w = 4, fb_h = 4;
+	GLuint render_tex, framebuf;
+	create_framebuffer(fb_w, fb_h, &render_tex, &framebuf);
 	glViewport(0, 0, fb_w, fb_h);
 
-
-
+	GLuint iResolution = glGetUniformLocation(s -> shader_program, "iResolution");
+	// TODO: error check?
+	glUniform3f(iResolution, (f32) fb_w, (f32) fb_h, 1.0f);
 
 	glClearColor(0.1f, 0.25f, 0.24f, 1);
 	glClear(GL_COLOR_BUFFER_BIT);
@@ -142,9 +159,13 @@ void render(Sdfps *s) {
 	);
 
 #if 1
-	// just here to check that it works, since it can be used as an easy way to
-	// get data back out of a shader, there's probs a more proper way to do it
-	// that we could change to later
+	/*
+	just here to check that it works, since it can be used as an easy way to
+	get data back out of a shader, there's probs a more proper way to do it
+	that we could change to later
+	UPDATE: looking at shader toy's source it seems it uses this function to
+	get output for sound shaders
+	*/
 	f32 pixels[16 * 16 * 4] = { 0.0f };
 	glReadPixels(
 		10, // x pixel starting bottom left,