From e9f7e9a4241d905153951cc15b302a8db39bcac4 Mon Sep 17 00:00:00 2001
From: Moritz Ruge <ruge.moritz@gmail.com>
Date: Thu, 6 Aug 2026 17:38:21 +0200
Subject: triangle exercise 2

---
 main.c | 34 +++++++++++++++++++++++++---------
 1 file changed, 25 insertions(+), 9 deletions(-)

(limited to 'main.c')

diff --git a/main.c b/main.c
index ff31c74..c4ef368 100644
--- a/main.c
+++ b/main.c
@@ -15,7 +15,7 @@ int main(void) {
     int w_width = 1280;
     int w_height = 820;
     int shader_success;
-    unsigned int VBO, VAO, EBO;
+    unsigned int VBO[2], VAO[2], EBO;
     // fragment shader
     unsigned int vertex_shader;
     unsigned int fragment_shader;
@@ -52,6 +52,13 @@ int main(void) {
 	 0.9f,  0.7f, 0.0f,  	// exercise 1 right
 	 0.7f,  0.7f, 0.0f,  	// exercise 1 left
     };
+
+    // exercise 2 
+    float verticies2[] = {
+	-1.0f, -1.0f, 0.0f,	// left
+	-0.8f, -1.0f, 0.0f,	// rigth
+	-0.9f, -0.8f, 0.0f	// top
+    };
     unsigned int indices[] = {
 	0, 1, 2,	// first triangle
 	2, 3, 1		// second triangle
@@ -137,15 +144,15 @@ int main(void) {
     // set up vertex data (and buffers) and configure vertex attributes
     // ----------------------------------------------------------------
     
-    glGenVertexArrays(1, &VAO);
-    glGenBuffers(1, &VBO);
+    glGenVertexArrays(2, VAO);
+    glGenBuffers(2, VBO);
     glGenBuffers(1, &EBO);
 
     // bind the vertex array object first, then bind and set vertex buffers, and then configure vertex attributes.
-    glBindVertexArray(VAO);
+    glBindVertexArray(VAO[0]);
 
     // 0. copy our vertices array in a buffer for OpenGL to use
-    glBindBuffer(GL_ARRAY_BUFFER, VBO);
+    glBindBuffer(GL_ARRAY_BUFFER, VBO[0]);
     glBufferData(GL_ARRAY_BUFFER, sizeof(verticies), verticies, GL_STATIC_DRAW);
 
     glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, EBO);
@@ -157,13 +164,20 @@ int main(void) {
     glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
     glEnableVertexAttribArray(0);
 
+    // exercise 2: 2 VAO VBO
+    glBindVertexArray(VAO[1]);
+    glBindBuffer(GL_ARRAY_BUFFER, VBO[1]);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(verticies2), verticies2, GL_STATIC_DRAW);
+    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 3 * sizeof(float), (void*)0);
+    glEnableVertexAttribArray(0);
+
     // note that this is allowed, the call to glVertexAttribPointer registered VBO as the vertex attribute's bound vertex buffer object so afterwards we can safely unbind
     glBindBuffer(GL_ARRAY_BUFFER, 0);
 
     glBindVertexArray(0);
 
     // uncomment this call to draw in wireframe polygons.
-    glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
+    //glPolygonMode(GL_FRONT_AND_BACK, GL_LINE);
 
     // -------------------------------------------------------------------------
     // render loop
@@ -184,9 +198,11 @@ int main(void) {
 
 	// render triangle
 	glUseProgram(shader_program);
-	glBindVertexArray(VAO);
+	glBindVertexArray(VAO[0]);
 	glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
 	glDrawArrays(GL_TRIANGLES, 4, 6);
+	glBindVertexArray(VAO[1]);
+	glDrawArrays(GL_TRIANGLES, 0, 3);
 
 	// check and call events and swap the buffers
 	// ------------------------------------------
@@ -195,8 +211,8 @@ int main(void) {
     }
 
     // de-allocate all resources
-    glDeleteVertexArrays(1, &VAO);
-    glDeleteBuffers(1, &VBO);
+    glDeleteVertexArrays(2, VAO);
+    glDeleteBuffers(2, VBO);
     glDeleteBuffers(1, &EBO);
     glDeleteProgram(shader_program);
 
-- 
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