u03-4

src/main.c

@@ -16,6 +16,8 @@ GLuint program;
 
 GLuint vertexArrayObject;
 
+GLuint indexBuffer;
+
 GLuint initialWindowWidth = 800;
 GLuint initialWindowHeight = 600;
 
@@ -112,98 +114,52 @@ void init(void) {
 	 * |     -0.2    0.2  |
 	 * |    |        |    |
 	 * 
-	 * +----+        +----+    ---  0.6
+	 * 0----1        4----5    ---  0.6
 	 * |    |        |    |    
 	 * |    |        |    |
-	 * |    +--------+    |    ---  0.1
+	 * |    2--------3    |    ---  0.1
 	 * |                  |
-	 * |    +--------+    |    --- -0.1
+	 * |    9--------8    |    --- -0.1
 	 * |    |        |    |
 	 * |    |        |    |
-	 * +----+        +----+    --- -0.6
+	 * 11---10       7----6    --- -0.6
 	 *
-	 * +------------------+    --- -0.7
+	 * 12-----------------13   --- -0.7
 	 * |                  |
-	 * +------------------+    --- -0.9
+	 * 15-----------------14    --- -0.9
 	 *   
 	 */    
 
 	GLfloat vertices[] = {
 		// X  // Y
-
-		// left vertical bar
-		-0.35f, -0.6f,
 		-0.35f, 0.6f,
 		-0.2f, 0.6f,
-
-		-0.35f, -0.6f,
-		-0.2f, 0.6f,
-		-0.2f, -0.6f,
-
-		// right vertical bar
-		0.35f, -0.6f,
-		0.35f, 0.6f,
-		0.2f, 0.6f,
-
-		0.35f, -0.6f,
-		0.2f, 0.6f,
-		0.2f, -0.6f,
-
-		// middle bar
-		-0.2f, -0.1f,
 		-0.2f, 0.1f,
 		0.2f, 0.1f,
-
-		-0.2f, -0.1f,
-		0.2f, 0.1f,
+		0.2f, 0.6f,
+		0.35f, 0.6f,
+		0.35f, -0.6f,
+		0.2f, -0.6f,
 		0.2f, -0.1f,
-
-		// bottom bar
-		-0.35f, -0.7f,
-		-0.35f, -0.9f,
-		0.35f, -0.9f,
+		-0.2f, -0.1f,
+		-0.2f, -0.6f,
+		-0.35f, -0.6f,
 
 		-0.35f, -0.7f,
+		0.35f, -0.7f,
 		0.35f, -0.9f,
-		0.35f, -0.7f
+		-0.35f, -0.9f
 	};
 
-	GLfloat colors[] = {
-		// R  // G  // B
-		1.0f, 0.0f, 0.0f,
-		1.0f, 0.0f, 0.3f,
-		1.0f, 0.3f, 0.0f,
+	GLuint restart = 128;
+	glEnable(GL_PRIMITIVE_RESTART);
+	glPrimitiveRestartIndex(restart);
 
-		1.0f, 0.3f, 0.3f,
-		1.0f, 0.3f, 0.6f,
-		1.0f, 0.6f, 0.3f,
-
-
-		0.0f, 1.0f, 0.0f,
-		0.0f, 1.0f, 0.3f,
-		0.3f, 1.0f, 0.0f,
-
-		0.3f, 1.0f, 0.3f,
-		0.3f, 1.0f, 0.6f,
-		0.6f, 1.0f, 0.3f,
-
-
-		0.3f, 0.3f, 1.0f,
-		0.3f, 0.6f, 1.0f,
-		0.6f, 0.3f, 1.0f,
-
-		0.3f, 0.3f, 1.0f,
-		0.3f, 0.6f, 1.0f,
-		0.6f, 0.3f, 1.0f,
-
-
-		1.0f, 1.0f, 0.0f,
-		1.0f, 1.0f, 0.1f,
-		1.0f, 1.0f, 0.2f,
-
-		1.0f, 1.0f, 0.7f,
-		1.0f, 1.0f, 0.8f,
-		1.0f, 1.0f, 0.9f
+	GLuint indices[] = {
+		1, 0, 10, 11, restart,
+		2, 3, 9, 8, restart,
+		5, 4, 6, 7, restart,
+		12, 13, 15, 14, restart
 	};
 
 	DEBUG("Creating vertext buffer");
@@ -213,13 +169,6 @@ void init(void) {
 	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
 	glBindBuffer(GL_ARRAY_BUFFER, 0);
 
-	DEBUG("Creating colour buffer");
-	GLuint colorBuffer;
-	glGenBuffers(1, &colorBuffer);
-	glBindBuffer(GL_ARRAY_BUFFER, colorBuffer);
-	glBufferData(GL_ARRAY_BUFFER, sizeof(colors), colors, GL_STATIC_DRAW);
-	glBindBuffer(GL_ARRAY_BUFFER, 0);
-
 	DEBUG("Creating vertex array object");
 	// create vertex array object
 	glGenVertexArrays(1, &vertexArrayObject);
@@ -237,12 +186,12 @@ void init(void) {
 	);
 	glEnableVertexAttribArray(0);
 
-	// vertex color data
-	glBindBuffer(GL_ARRAY_BUFFER, colorBuffer);
-	glVertexAttribPointer(1, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(GLfloat), 0);
-	glEnableVertexAttribArray(1);
-
+	DEBUG("Creating index buffer");
+	glGenBuffers(1, &indexBuffer);
+	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
+	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
 
+	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
 	glBindBuffer(GL_ARRAY_BUFFER, 0);
 	glBindVertexArray(0);
 
@@ -269,7 +218,8 @@ void draw(void) {
 	glUniform2f(positionLocation, cos(currentHue * 2 * M_PI) * 0.2f, sin(currentHue * 2 * M_PI) * 0.2f);
 
 	glBindVertexArray(vertexArrayObject);
-	glDrawArrays(GL_TRIANGLES, 0, 48);
+	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, indexBuffer);
+	glDrawElements(GL_TRIANGLE_STRIP, 20, GL_UNSIGNED_INT, 0);
 }
 
 void framebuffer_size_callback(GLFWwindow* window, int width, int height) {

src/shaders/vertex.glsl

@@ -1,11 +1,10 @@
 #version 330 core
 layout (location = 0) in vec2 aPosition;
-layout (location = 1) in vec3 aColor;
 uniform vec2 uPosition;
 
 out vec3 vertexColor;
 
 void main() {
-	vertexColor = aColor;
+	vertexColor = vec3(1.0, 0.1, 0.1);
 	gl_Position = vec4(uPosition + aPosition, 0.0, 1.0);
 }