learn opengl

build.sh

@@ -2,8 +2,8 @@
 
 set -xe
 
-CFLAGS="-Wall -Wextra $(pkg-config --cflags sdl2 glew)"
-LIBS="$(pkg-config --libs sdl2 glew)"
+CFLAGS="-g -Wall -Wextra $(pkg-config --cflags sdl2 glew)"
+LIBS="$(pkg-config --libs sdl2 glew) -lm"
 
 # gcc -Wall -Wextra -o gameoflife_term gameoflife_term.c
-gcc ${CFLAGS} -o gameoflife_graph gameoflife_graph.c ${LIBS}
+gcc ${CFLAGS} -o opengl_train opengl_train.c ${LIBS}

opengl_train.c

@@ -1,11 +1,12 @@
-#include <SDL2/SDL_events.h>
 #include <GL/glew.h>
 #include <SDL2/SDL.h>
 #include <SDL2/SDL_opengl.h>
-#include <SDL2/SDL_opengl_glext.h>
 #include <stdbool.h>
 #include <stdio.h>
 
+#define STB_IMAGE_IMPLEMENTATION
+#include "stb_image.h"
+
 #define FACTOR 80
 #define WIDTH ((FACTOR) * 16)
 #define HEIGHT ((FACTOR) * 9)
@@ -13,9 +14,16 @@
 SDL_Event e;
 
 float vertices[] = {
-	0.0f, 0.5f,
-	0.5f, -0.5f,
-	-0.5f, -0.5f
+	// Positions	Color				TexCoords
+    -0.5f,  0.5f,	1.0f, 0.0f, 0.0f,	0.0f, 0.0f, // Top-left
+     0.5f,  0.5f,	0.0f, 1.0f, 0.0f,	1.0f, 0.0f, // Top-right
+     0.5f, -0.5f,	0.0f, 0.0f, 1.0f,	1.0f, 1.0f, // Bottom-right
+    -0.5f, -0.5f,	1.0f, 1.0f, 1.0f,	0.0f, 1.0f, // Bottom-left
+};
+
+GLuint elements[] = {
+	0, 1, 2,
+	2, 3, 0,
 };
 
 char * read_file(const char* path){
@@ -88,26 +96,76 @@ int main(void)
 	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MAJOR_VERSION, 3);
 	SDL_GL_SetAttribute(SDL_GL_CONTEXT_MINOR_VERSION, 2);
 
+	// vectors
 	GLuint vertexBuffer;
 	glGenBuffers(1, &vertexBuffer);
 	glBindBuffer(GL_ARRAY_BUFFER, vertexBuffer);
 
 	glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
 
+	// reuse vectors
+	GLuint ebo;
+	glGenBuffers(1, &ebo);
+	glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
+	glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(elements), elements, GL_STATIC_DRAW);
+
 	GLuint vertexShader = CompileShader(vs, GL_VERTEX_SHADER);
 	GLuint fragmentShader = CompileShader(fs, GL_FRAGMENT_SHADER);
 	GLuint shaderProgram = LinkShader(vertexShader, fragmentShader);
 
+	// Textures
+	int width, height;
+	unsigned char *image, *image2;
+
+	GLuint tex[2];
+	glGenTextures(2, tex);
+
+	glActiveTexture(GL_TEXTURE0);
+	glBindTexture(GL_TEXTURE_2D, tex[0]);
+
+	//Load image
+	image = stbi_load("./sample.png", &width, &height, NULL, 3);
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, image);
+	stbi_image_free(image);
+	glGenerateMipmap(GL_TEXTURE_2D);
+
+	glUniform1i(glGetUniformLocation(shaderProgram, "kitty"), 0);
+
+	glActiveTexture(GL_TEXTURE1);
+	glBindTexture(GL_TEXTURE_2D, tex[1]);
+
+	//Load image
+	image2 = stbi_load("./sample2.png", &width, &height, NULL, 3);
+	glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, width, height, 0, GL_RGB, GL_UNSIGNED_BYTE, image2);
+	stbi_image_free(image2);
+	glGenerateMipmap(GL_TEXTURE_2D);
+
+	glUniform1i(glGetUniformLocation(shaderProgram, "puppy"), 1);
+
 	GLint posAttrib = glGetAttribLocation(shaderProgram, "positions");
 	glEnableVertexAttribArray(posAttrib);
-	glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 0, 0);
+	glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 7, 0);
 
+	GLint colAttrib = glGetAttribLocation(shaderProgram, "color");
+	glEnableVertexAttribArray(colAttrib);
+	glVertexAttribPointer(colAttrib, 3, GL_FLOAT, GL_FALSE, sizeof(float) * 7, (void*)(2*sizeof(float)));
+
+	GLint texCoordsAttrib = glGetAttribLocation(shaderProgram, "texCoords");
+	glEnableVertexAttribArray(texCoordsAttrib);
+	glVertexAttribPointer(texCoordsAttrib, 2, GL_FLOAT, GL_FALSE, sizeof(float) * 7, (void*)(5*sizeof(float)));
+
+	glUseProgram(shaderProgram);
+
+	int i = 0;
 	bool should_close = false;
 	while(!should_close){
+		i++;
 		glClearColor(0, 0, 0, 1);
 		glClear(GL_COLOR_BUFFER_BIT);
+		glUniform1i(glGetUniformLocation(shaderProgram, "triangleColor"), i);
 
-		glDrawArrays(GL_TRIANGLES, 0, 3);
+		glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
+		/* glDrawArrays(GL_TRIANGLES, 0, 3); */
 
 		SDL_GL_SwapWindow(win);
 
@@ -121,8 +179,6 @@ int main(void)
 	glDeleteShader(fragmentShader);
 	glDeleteShader(vertexShader);
 
-	glDeleteBuffers(1, &vertexBuffer);
-
 	SDL_GL_DeleteContext(con);
 	SDL_DestroyWindow(win);
 	SDL_Quit();

shader.fs

@@ -1,7 +1,19 @@
 #version 330 core
 
+in vec3 Color;
+in vec2 TexCoords;
+
+uniform int triangleColor;
+
+uniform sampler2D kitty;
+uniform sampler2D puppy;
+
 out vec4 outColor;
 
 void main(){
-	outColor = vec4(1.0, 1.0, 1.0, 1.0);
+	vec4 kit = texture(kitty, TexCoords);
+	vec4 pup = texture(puppy, TexCoords);
+	outColor = pup;
 }
+
+/* vim: set ft=glsl: */

shader.vs

@@ -1,7 +1,16 @@
 #version 330 core
 
 in vec2 positions;
+in vec3 color;
+in vec2 texCoords;
+
+out vec3 Color;
+out vec2 TexCoords;
 
 void main(){
+	Color = color;
+	TexCoords = texCoords;
 	gl_Position = vec4(positions, 0.0, 1.0);
 }
+
+// vim: set ft=glsl: