From 56cf731b7f17bfb4201123ff95e36b1e668cf41f Mon Sep 17 00:00:00 2001
From: Luca Giuliano Conte <main@lugico.de>
Date: Thu, 4 Apr 2024 14:05:28 +0200
Subject: [PATCH] add backface culling

---
 u03-4/main.c            | 27 +++++++++++++++++++++++----
 u03-4/vertexShader.c    | 13 +++++++++----
 u03-4/vertexShader.glsl |  3 ++-
 3 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/u03-4/main.c b/u03-4/main.c
index 419e0e3..4865887 100644
--- a/u03-4/main.c
+++ b/u03-4/main.c
@@ -40,6 +40,8 @@ typedef struct {
 GLuint program;
 GLuint vao;
 
+GLfloat rotation;
+
 void init(void) {
 
 	// create and compile vertex shader
@@ -87,6 +89,10 @@ void init(void) {
 		printf("%s",infoLog);
 	}
 
+	free(fragmentText);
+	fragmentText = NULL;
+	fragmentTextConst = NULL;
+
 	// create and link shader program
 	program = glCreateProgram();
 	glAttachShader(program, vertexShader);
@@ -214,6 +220,7 @@ void init(void) {
 	glBindBuffer(GL_ARRAY_BUFFER, 0);
 	glBindVertexArray(0);
 
+
 	glClearColor(0.2f, 0.3f, 0.3f, 1.0f);
 }
 
@@ -222,11 +229,22 @@ void draw(void) {
 	glUseProgram(program);
 	glBindVertexArray(vao);
 
+	rotation = rotation + 0.01f;
+	if (rotation > 2 * 3.1415926f) {
+		rotation = 0;
+	}
+
+	glUniform1f(glGetUniformLocation(program, "rotation"), rotation);
+
+	glFrontFace(GL_CW);
+	glCullFace(GL_BACK);
+	glEnable(GL_CULL_FACE);
+
 
 	glEnable(GL_PRIMITIVE_RESTART);
 	glPrimitiveRestartIndex(RESTART);
 
-	GLuint indices[] = {0, 1, 2, 3, RESTART, 4, 5, 6, 7, RESTART, 8, 9, 10, 11, RESTART, 12, 13, 14, 15};
+	GLuint indices[] = {0, 1, 2, 3, RESTART, 4, 6, 5, 7, RESTART, 8, 9, 10, 11, RESTART, 12, 14, 13, 15};
 
 	glDrawElements(GL_TRIANGLE_STRIP, sizeof(indices) / sizeof(GLuint),  GL_UNSIGNED_INT, indices);
 }
@@ -236,14 +254,12 @@ void framebuffer_size_callback(GLFWwindow *window, int width, int height) {
 }
 
 int main(void) {
-	printf("Hello World!\n");
-
 	glfwInit();
 	glfwWindowHint(GLFW_CONTEXT_VERSION_MAJOR, 3);
 	glfwWindowHint(GLFW_CONTEXT_VERSION_MINOR, 3);
 	glfwWindowHint(GLFW_OPENGL_PROFILE, GLFW_OPENGL_CORE_PROFILE);
 
-	GLFWwindow *window = glfwCreateWindow(800, 800, "Computergrafik 1", NULL, NULL);
+	GLFWwindow *window = glfwCreateWindow(600, 600, "Computergrafik 1", NULL, NULL);
 
 	if (!window) {
 		printf("Failed to create window\n");
@@ -257,6 +273,9 @@ int main(void) {
 
 	glewInit();
 
+	printf("OpenGL version supported by this platform (%s):\n", glGetString(GL_VERSION));
+
+
 	init();
 
 	while (!glfwWindowShouldClose(window)) {
diff --git a/u03-4/vertexShader.c b/u03-4/vertexShader.c
index f8c9d17..5ce5d3e 100644
--- a/u03-4/vertexShader.c
+++ b/u03-4/vertexShader.c
@@ -7,7 +7,9 @@ unsigned char vertexShader_glsl[] = {
   0x61, 0x79, 0x6f, 0x75, 0x74, 0x20, 0x28, 0x6c, 0x6f, 0x63, 0x61, 0x74,
   0x69, 0x6f, 0x6e, 0x20, 0x3d, 0x20, 0x31, 0x29, 0x20, 0x69, 0x6e, 0x20,
   0x66, 0x6c, 0x6f, 0x61, 0x74, 0x20, 0x76, 0x65, 0x72, 0x74, 0x65, 0x78,
-  0x56, 0x61, 0x6c, 0x75, 0x65, 0x3b, 0x0a, 0x6f, 0x75, 0x74, 0x20, 0x66,
+  0x56, 0x61, 0x6c, 0x75, 0x65, 0x3b, 0x0a, 0x75, 0x6e, 0x69, 0x66, 0x6f,
+  0x72, 0x6d, 0x20, 0x66, 0x6c, 0x6f, 0x61, 0x74, 0x20, 0x72, 0x6f, 0x74,
+  0x61, 0x74, 0x69, 0x6f, 0x6e, 0x3b, 0x0a, 0x6f, 0x75, 0x74, 0x20, 0x66,
   0x6c, 0x6f, 0x61, 0x74, 0x20, 0x66, 0x72, 0x61, 0x67, 0x6d, 0x65, 0x6e,
   0x74, 0x56, 0x61, 0x6c, 0x75, 0x65, 0x3b, 0x0a, 0x76, 0x6f, 0x69, 0x64,
   0x20, 0x6d, 0x61, 0x69, 0x6e, 0x28, 0x29, 0x20, 0x7b, 0x0a, 0x09, 0x66,
@@ -15,7 +17,10 @@ unsigned char vertexShader_glsl[] = {
   0x20, 0x3d, 0x20, 0x76, 0x65, 0x72, 0x74, 0x65, 0x78, 0x56, 0x61, 0x6c,
   0x75, 0x65, 0x3b, 0x0a, 0x09, 0x67, 0x6c, 0x5f, 0x50, 0x6f, 0x73, 0x69,
   0x74, 0x69, 0x6f, 0x6e, 0x20, 0x3d, 0x20, 0x76, 0x65, 0x63, 0x34, 0x28,
-  0x61, 0x50, 0x6f, 0x73, 0x69, 0x74, 0x69, 0x6f, 0x6e, 0x2c, 0x20, 0x30,
-  0x2e, 0x30, 0x2c, 0x20, 0x31, 0x2e, 0x30, 0x29, 0x3b, 0x0a, 0x7d
+  0x61, 0x50, 0x6f, 0x73, 0x69, 0x74, 0x69, 0x6f, 0x6e, 0x2e, 0x78, 0x20,
+  0x2a, 0x20, 0x73, 0x69, 0x6e, 0x28, 0x72, 0x6f, 0x74, 0x61, 0x74, 0x69,
+  0x6f, 0x6e, 0x29, 0x2c, 0x20, 0x61, 0x50, 0x6f, 0x73, 0x69, 0x74, 0x69,
+  0x6f, 0x6e, 0x2e, 0x79, 0x2c, 0x20, 0x30, 0x2e, 0x30, 0x2c, 0x20, 0x31,
+  0x2e, 0x30, 0x29, 0x3b, 0x0a, 0x7d
 };
-unsigned int vertexShader_glsl_len = 215;
+unsigned int vertexShader_glsl_len = 270;
diff --git a/u03-4/vertexShader.glsl b/u03-4/vertexShader.glsl
index 8796192..abdb1a5 100644
--- a/u03-4/vertexShader.glsl
+++ b/u03-4/vertexShader.glsl
@@ -1,8 +1,9 @@
 #version 330 core
 layout (location = 0) in vec2 aPosition;
 layout (location = 1) in float vertexValue;
+uniform float rotation;
 out float fragmentValue;
 void main() {
 	fragmentValue = vertexValue;
-	gl_Position = vec4(aPosition, 0.0, 1.0);
+	gl_Position = vec4(aPosition.x * sin(rotation), aPosition.y, 0.0, 1.0);
 }
\ No newline at end of file