fragment shader demo working :tada:

2 files changed, 18 insertions, 22 deletions

diff --git a/hello.frag b/hello.frag
index a804a77..291c0f1 100644
--- a/hello.frag
+++ b/hello.frag
@@ -1,13 +1,9 @@
 #version 330 core
-out vec4 FragColor;
+
+#define WIDTH 800
+#define HEIGHT 600
 
 void main() {
-	FragColor = vec4(1.0f, 0.5f, 0.2f, 1.0f);
+	gl_FragColor = vec4(gl_FragCoord.x / WIDTH, gl_FragCoord.y / HEIGHT, 0, 1);
 }
 
-// #version 330 core
-//
-// void main() {
-//   gl_FragColor = vec4(gl_FragCoord.xy, 0, 1);
-// }
-//
diff --git a/main.c b/main.c
index 8ac0ca2..c7a156b 100644
--- a/main.c
+++ b/main.c
@@ -8,18 +8,19 @@
 #include "hello_vert.h"
 #include "hello_frag.h"
 
-void prepare_tri(GLuint* VBO, GLuint* VAO) {
+void prepare_tri() {
 	const float vertices[] = {
-		-0.5f, -0.5f, 0.0f,
-		0.5f, -0.5f, 0.0f,
-		0.0f,  0.5f, 0.0f,
+		-1, -1, 0,
+		3, -1, 0,
+		-1, 3, 0,
 	};
 
 	// initialize vertex {buffer,attribute} object buffers
-	glGenBuffers(1, VBO);
-	glBindBuffer(GL_ARRAY_BUFFER, *VBO);
-	glGenBuffers(1, VAO);
-	glBindVertexArray(*VAO);
+	GLuint VBO, VAO;
+	glGenBuffers(1, &VBO);
+	glBindBuffer(GL_ARRAY_BUFFER, VBO);
+	glGenVertexArrays(1, &VAO);
+	glBindVertexArray(VAO);
 
 	// copy vertex data into VBO
 	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
@@ -27,6 +28,10 @@ void prepare_tri(GLuint* VBO, GLuint* VAO) {
 	// set VAO pointers
 	glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
 	glEnableVertexAttribArray(0);
+
+	// draw (only) this triangle
+	glBindBuffer(GL_ARRAY_BUFFER, 0);
+	glBindVertexArray(VAO);
 }
 
 int main(int argc, char** argv) {
@@ -49,8 +54,7 @@ int main(int argc, char** argv) {
 	glewInit();
 
 	// create single triangle
-	GLuint VBO, VAO;
-	prepare_tri(&VBO, &VAO);
+	prepare_tri();
 
 	// prepare shaders
 	GLuint shader = link_shaders(
@@ -62,11 +66,7 @@ int main(int argc, char** argv) {
 	while (!glfwWindowShouldClose(window)) {
 		glfwPollEvents();
 
-		glClearColor(1.f, 0.f, 1.f, 1.0f);
-		glClear(GL_COLOR_BUFFER_BIT);
-
 		glUseProgram(shader);
-		glBindVertexArray(VAO);
 		glDrawArrays(GL_TRIANGLES, 0, 3);
 
 		glfwSwapBuffers(window);