I understand vaos

opengl/TODO.md

@@ -155,3 +155,7 @@ E.g. Vertex Array Object is a container <https://www.opengl.org/wiki/Vertex_Spec
 TODO.
 
 <http://stackoverflow.com/questions/6682771/gldrawelements-vs-gldrawarray-efficiency>
+
+If the last argument of glDrawElements is null, it takes the currently bound:
+
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);

opengl/glfw_color_array.c

@@ -51,12 +51,16 @@ int main(void) {
     attribute_position = glGetAttribLocation(program, "position");
     attribute_vertColor = glGetAttribLocation(program, "vertColor");
 
-    /* Buffer setup. */
+    /* vbo */
-    glGenVertexArrays(1, &vao);
     glGenBuffers(1, &vbo);
-    glBindVertexArray(vao);
     glBindBuffer(GL_ARRAY_BUFFER, vbo);
     glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+    /* Buffer setup. */
+    glGenVertexArrays(1, &vao);
+    glBindVertexArray(vao);
+    glBindBuffer(GL_ARRAY_BUFFER, vbo);
     glVertexAttribPointer(
         attribute_position,
         3,

opengl/glfw_texture.c

@@ -46,6 +46,7 @@ int main(void) {
         program,
         texture,
         uvbo,
+        vao,
         vbo
     ;
     unsigned int
@@ -66,7 +67,6 @@ int main(void) {
     coord2d_location = glGetAttribLocation(program, "coord2d");
     vertexUv_location = glGetAttribLocation(program, "vertexUv");
 	myTextureSampler_location = glGetUniformLocation(program, "myTextureSampler");
-    glUseProgram(program);
 
     /* vbo */
     glGenBuffers(1, &vbo);
@@ -85,9 +85,13 @@ int main(void) {
         texture_image = common_texture_get_image(texture_width, texture_height);
         glGenTextures(1, &texture);
         glBindTexture(GL_TEXTURE_2D, texture);
+        glActiveTexture(GL_TEXTURE0);
+
+        /* Specify data for current texture unit specified by glActiveTexture. */
         glTexImage2D(GL_TEXTURE_2D, 0, GL_RGB, texture_width, texture_width,
                      0, GL_BGR, GL_UNSIGNED_BYTE, texture_image);
 
+        /* glTexParameter specifies parameters for the current texture unit. */
         /* Cheap. filtering. */
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_NEAREST);
         glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_NEAREST);
@@ -102,42 +106,25 @@ int main(void) {
         free(texture_image);
     }
 
-    /* vbo */
+    glGenVertexArrays(1, &vao);
+    glBindVertexArray(vao);
     glBindBuffer(GL_ARRAY_BUFFER, vbo);
-    glVertexAttribPointer(
+    glVertexAttribPointer(coord2d_location, 2, GL_FLOAT, GL_FALSE, 0, 0);
-        coord2d_location,
+    glEnableVertexAttribArray(coord2d_location);
-        2,
-        GL_FLOAT,
-        GL_FALSE,
-        0,
-        0
-    );
-    glBindBuffer(GL_ARRAY_BUFFER, 0);
-
-    /* uvbo */
     glBindBuffer(GL_ARRAY_BUFFER, uvbo);
-    glVertexAttribPointer(
+    glVertexAttribPointer(vertexUv_location, 2, GL_FLOAT, GL_FALSE, 0, 0);
-        vertexUv_location,
+    glEnableVertexAttribArray(vertexUv_location);
-        2,
+    glBindVertexArray(0);
-        GL_FLOAT,
-        GL_FALSE,
-        0,
-        0
-    );
-    glBindBuffer(GL_ARRAY_BUFFER, 0);
 
     /* Draw. */
     glViewport(0, 0, WIDTH, HEIGHT);
     glClearColor(1.0f, 1.0f, 1.0f, 1.0f);
     glClear(GL_COLOR_BUFFER_BIT);
-    glActiveTexture(GL_TEXTURE0);
     /* Sampler will sample from GL_TEXTURE0. TODO example that changes this. */
-    glUniform1i(myTextureSampler_location, 0);
+    glUseProgram(program);
-    glEnableVertexAttribArray(coord2d_location);
+    glBindVertexArray(vao);
-    glEnableVertexAttribArray(vertexUv_location);
     glDrawArrays(GL_TRIANGLES, 0, 3);
-    glDisableVertexAttribArray(coord2d_location);
+    glBindVertexArray(0);
-    glDisableVertexAttribArray(vertexUv_location);
     glfwSwapBuffers(window);
 
     /* Main loop. */
@@ -148,6 +135,7 @@ int main(void) {
     /* Cleanup. */
     glDeleteBuffers(1, &vbo);
     glDeleteBuffers(1, &uvbo);
+    glDeleteVertexArrays(1, &vao);
 	glDeleteTextures(1, &texture);
     glDeleteProgram(program);
     glfwTerminate();

opengl/glfw_transform.c

@@ -57,28 +57,33 @@ int main(void) {
     glewExperimental = GL_TRUE;
     glewInit();
 
-    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+    /* Shader program. */
-    glViewport(0, 0, WIDTH, HEIGHT);
-
-    /* Shaders. */
     program = common_get_shader_program(vertex_shader_source, fragment_shader_source);
     vColor_location = glGetAttribLocation(program, "vColor");
     position_location = glGetAttribLocation(program, "position");
     transform_location = glGetUniformLocation(program, "transform");
     glUseProgram(program);
 
-    /* Buffers. */
+    /* vbo */
-    glGenVertexArrays(1, &vao);
     glGenBuffers(1, &vbo);
-    glBindVertexArray(vao);
     glBindBuffer(GL_ARRAY_BUFFER, vbo);
     glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
-    /* Position attribute */
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+    /* Buffers. */
+    glGenVertexArrays(1, &vao);
+    glBindVertexArray(vao);
+    glBindBuffer(GL_ARRAY_BUFFER, vbo);
     glVertexAttribPointer(position_location, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)0);
-    /* Color attribute */
+    glEnableVertexAttribArray(position_location);
     glVertexAttribPointer(vColor_location, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)(3 * sizeof(GLfloat)));
+    glEnableVertexAttribArray(vColor_location);
     glBindVertexArray(0);
 
+    /* Global draw calls. */
+    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+    glViewport(0, 0, WIDTH, HEIGHT);
+
     /* Main loop. */
     common_fps_init();
     while (!glfwWindowShouldClose(window)) {
@@ -92,11 +97,7 @@ int main(void) {
         glUniformMatrix4fv(transform_location, 1, GL_FALSE, transform);
 
         glBindVertexArray(vao);
-        glEnableVertexAttribArray(position_location);
-        glEnableVertexAttribArray(vColor_location);
         glDrawArrays(GL_TRIANGLES, 0, 3);
-        glDisableVertexAttribArray(position_location);
-        glDisableVertexAttribArray(vColor_location);
         glBindVertexArray(0);
 
         glfwSwapBuffers(window);

opengl/glfw_triangle_vao.c

@@ -18,11 +18,20 @@ Looks like a way to bind a bunch of things at once:
 > stores all of the state needed to supply vertex data (with one minor exception noted below).
 It stores the format of the vertex data as well as the Buffer Objects
 
+What is stores:
+
+- glBind calls
+- glVertexAttribPointer and glEnableVertexAttribArray calls TODO: why not store shaders as well then, since those are bound to shaders?
+
 VAO is a container object: it contains other objects.
 https://www.opengl.org/wiki/Vertex_Specification#Vertex_Array_Object
 
 Adapted from
 https://github.com/JoeyDeVries/LearnOpenGL/blob/d5c3be70ab2b884cf2b2c94cbf73a31f632fbf47/src/1.getting_started/2.hello_triangle/hellotriangle2.cpp
+
+Tood explanations:
+
+- http://www.learnopengl.com/#!Getting-Started/Hello-Triangle
 */
 
 #include "common.h"
@@ -60,25 +69,28 @@ int main(void) {
     glfwMakeContextCurrent(window);
     glewInit();
 
+    /* Shader. */
     program = common_get_shader_program(vertex_shader_source, fragment_shader_source);
     attribute_position = glGetAttribLocation(program, "position");
 
-    /* Buffer setup. */
-    glGenVertexArrays(1, &vao);
     glGenBuffers(1, &vbo);
-    glBindVertexArray(vao);
     glBindBuffer(GL_ARRAY_BUFFER, vbo);
     glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+    /* Buffer setup. */
+    glGenVertexArrays(1, &vao);
+    glBindVertexArray(vao);
+    glBindBuffer(GL_ARRAY_BUFFER, vbo);
     glVertexAttribPointer(attribute_position, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);
     glEnableVertexAttribArray(0);
-    glBindBuffer(GL_ARRAY_BUFFER, 0);
     glBindVertexArray(0);
 
     /* Draw. */
-    glUseProgram(program);
-    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
     glViewport(0, 0, WIDTH, HEIGHT);
+    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
     glClear(GL_COLOR_BUFFER_BIT);
+    glUseProgram(program);
     glBindVertexArray(vao);
     glDrawArrays(GL_TRIANGLES, 0, 3);
     glBindVertexArray(0);

opengl/glfw_triangle_vbo.c

@@ -63,7 +63,12 @@ int main(void) {
         */
         /* vertices[0] = 1.0; */
 
-        /* Set currently bound GL_ARRAY_BUFFER as the vertex shader input. */
+        /*
+        Set currently bound GL_ARRAY_BUFFER as the vertex shader input.
+
+        -   argument 2: size. Can only be 1, 2, 3, or 4. Each one of those maps to a
+            vec1, 2, 3 or 4 argument in the shader.
+        */
         glVertexAttribPointer(attribute_coord2d, 2, GL_FLOAT, GL_FALSE, 0, 0);
 
         /* Unbind GL_ARRAY_BUFFER. */

opengl/glfw_triangles.c

@@ -4,8 +4,8 @@ Reuse vertices on multiple triangles via vertex indices.
 
 #include "common.h"
 
-static const GLuint WIDTH = 800;
+static const GLuint WIDTH = 500;
-static const GLuint HEIGHT = 600;
+static const GLuint HEIGHT = 500;
 /* ourColor is passed on to the fragment shader. */
 static const GLchar *vertex_shader_source =
     "#version 330 core\n"
@@ -46,7 +46,6 @@ int main(void) {
     glfwWindowHint(GLFW_RESIZABLE, GL_FALSE);
     GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, __FILE__, NULL, NULL);
     glfwMakeContextCurrent(window);
-    glewExperimental = GL_TRUE;
     glewInit();
 
     /* Shader program. */
@@ -54,20 +53,23 @@ int main(void) {
     attribute_position = glGetAttribLocation(program, "position");
     attribute_color = glGetAttribLocation(program, "color");
 
-    /* Buffer setup. */
+    /* vbo */
-    glGenVertexArrays(1, &vao);
     glGenBuffers(1, &vbo);
-    glGenBuffers(1, &ebo);
-    glBindVertexArray(vao);
     glBindBuffer(GL_ARRAY_BUFFER, vbo);
     glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+    /* ebo */
+    glGenBuffers(1, &ebo);
     glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
     glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
-    /*
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
-    Position attribute.
+
-    - 3: length
+    /* Buffer setup. */
-    - 6: how many bytes to skip until next one == 3 (position) + 3 (color)
+    glGenVertexArrays(1, &vao);
-    */
+    glBindVertexArray(vao);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
+    glBindBuffer(GL_ARRAY_BUFFER, vbo);
     glVertexAttribPointer(attribute_position, 3, GL_FLOAT, GL_FALSE, 6 * sizeof(GLfloat), (GLvoid*)0);
     glEnableVertexAttribArray(attribute_position);
     /* Color attribute */

opengl/glfw_webcam_image_process.c

@@ -130,7 +130,7 @@ static const GLchar *fragment_shader_source2 =
     /*"    color = texture(myTextureSampler, fragmentUv.yx ).rgb;\n"*/
 
     /*"// Inverter\n"*/
-    /*"    color = 1.0 - texture(myTextureSampler, fragmentUv.yx ).rgb;\n"*/
+    "    color = 1.0 - texture(myTextureSampler, fragmentUv.yx ).rgb;\n"
 
     /*"// Swapper\n"*/
     /*"    color = texture(myTextureSampler, fragmentUv.yx ).gbr;\n"*/
@@ -154,17 +154,17 @@ static const GLchar *fragment_shader_source2 =
     /*"    color /= blur_width;\n"*/
 
     /*"// Square linear blur. Good GPU bogger since n^2.\n"*/
-    "    int blur_width = 23;\n"
+    /*"    int blur_width = 23;\n"*/
-    "    int blur_width_half = blur_width / 2;\n"
+    /*"    int blur_width_half = blur_width / 2;\n"*/
-    "    color = vec3(0.0, 0.0, 0.0);\n"
+    /*"    color = vec3(0.0, 0.0, 0.0);\n"*/
-    "    for (int i = -blur_width_half; i <= blur_width_half; ++i) {\n"
+    /*"    for (int i = -blur_width_half; i <= blur_width_half; ++i) {\n"*/
-    "       for (int j = -blur_width_half; j <= blur_width_half; ++j) {\n"
+    /*"       for (int j = -blur_width_half; j <= blur_width_half; ++j) {\n"*/
-    "           color += texture(\n"
+    /*"           color += texture(\n"*/
-    "               myTextureSampler, fragmentUv.yx + ivec2(i, j) * pixD\n"
+    /*"               myTextureSampler, fragmentUv.yx + ivec2(i, j) * pixD\n"*/
-    "           ).rgb;\n"
+    /*"           ).rgb;\n"*/
-    "       }\n"
+    /*"       }\n"*/
-    "    }\n"
+    /*"    }\n"*/
-    "    color /= (blur_width * blur_width);\n"
+    /*"    color /= (blur_width * blur_width);\n"*/
 
     "}\n";
 
@@ -186,7 +186,8 @@ int main(int argc, char **argv) {
         program2,
         texture,
         vbo,
-        vao
+        vao,
+        vao2
     ;
     unsigned int
         cpu,
@@ -240,23 +241,37 @@ int main(int argc, char **argv) {
 	myTextureSampler_location2 = glGetUniformLocation(program2, "myTextureSampler");
 	pixD_location2 = glGetUniformLocation(program2, "pixD");
 
-    /* Buffer setup. */
+    /* Create vbo. */
-    glGenVertexArrays(1, &vao);
     glGenBuffers(1, &vbo);
-    glGenBuffers(1, &ebo);
-    glBindVertexArray(vao);
     glBindBuffer(GL_ARRAY_BUFFER, vbo);
     glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+
+    /* Create ebo. */
+    glGenBuffers(1, &ebo);
     glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
     glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(indices), indices, GL_STATIC_DRAW);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, 0);
+
+    /* vao. */
+    glGenVertexArrays(1, &vao);
+    glBindVertexArray(vao);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
+    glBindBuffer(GL_ARRAY_BUFFER, vbo);
     glVertexAttribPointer(coord2d_location, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(vertices[0]), (GLvoid*)0);
-    glVertexAttribPointer(coord2d_location2, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(vertices[0]), (GLvoid*)0);
     glEnableVertexAttribArray(coord2d_location);
-    /* TODO this likely makes no sense. Do we need 2 vaos? */
-    glEnableVertexAttribArray(coord2d_location2);
     glVertexAttribPointer(vertexUv_location, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (GLvoid*)(2 * sizeof(vertices[0])));
-    glVertexAttribPointer(vertexUv_location2, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (GLvoid*)(2 * sizeof(vertices[0])));
     glEnableVertexAttribArray(vertexUv_location);
+    glBindVertexArray(0);
+
+    /* vao2. */
+    glGenVertexArrays(1, &vao2);
+    glBindVertexArray(vao2);
+    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, ebo);
+    glBindBuffer(GL_ARRAY_BUFFER, vbo);
+    glVertexAttribPointer(coord2d_location2, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(vertices[0]), (GLvoid*)0);
+    glEnableVertexAttribArray(coord2d_location2);
+    glVertexAttribPointer(vertexUv_location2, 2, GL_FLOAT, GL_FALSE, 4 * sizeof(GLfloat), (GLvoid*)(2 * sizeof(vertices[0])));
     glEnableVertexAttribArray(vertexUv_location2);
     glBindVertexArray(0);
 
@@ -279,21 +294,18 @@ int main(int argc, char **argv) {
         CommonV4l2_updateImage(&common_v4l2);
         image = CommonV4l2_getImage(&common_v4l2);
         glClear(GL_COLOR_BUFFER_BIT);
-        glBindVertexArray(vao);
 
         /* Original. */
-        glUseProgram(program);
-        glUniform1i(myTextureSampler_location, 0);
         glTexImage2D(
             GL_TEXTURE_2D, 0, GL_RGB, width, height,
             0, GL_RGB, GL_UNSIGNED_BYTE, image
         );
+        glUseProgram(program);
+        glUniform1i(myTextureSampler_location, 0);
+        glBindVertexArray(vao);
         glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
+        glBindVertexArray(0);
 
-        /* Modified. */
-        glUseProgram(program2);
-        glUniform1i(myTextureSampler_location2, 0);
-        glUniform2f(pixD_location2, 1.0 / width, 1.0 / height);
         /* Optional CPU modification to compare with GPU shader speed.  */
         if (cpu) {
             image2 = realloc(image2, 3 * width * height * sizeof(image2[0]));
@@ -302,16 +314,17 @@ int main(int argc, char **argv) {
                     size_t index = 3 * (i * width + j);
 
                     /* Inverter. */
-                    /*image2[index + 0] = 255U - image[index + 0];*/
+                    image2[index + 0] = 1.0 - (image[index + 0] / 255.0);
-                    /*image2[index + 1] = 255U - image[index + 1];*/
+                    image2[index + 1] = 1.0 - (image[index + 1] / 255.0);
-                    /*image2[index + 2] = 255U - image[index + 2];*/
+                    image2[index + 2] = 1.0 - (image[index + 2] / 255.0);
 
                     /* Swapper. */
-                    /*image2[index + 0] = image[index + 1];*/
+                    /*image2[index + 0] = image[index + 1] / 255.0;*/
-                    /*image2[index + 1] = image[index + 2];*/
+                    /*image2[index + 1] = image[index + 2] / 255.0;*/
-                    /*image2[index + 2] = image[index + 0];*/
+                    /*image2[index + 2] = image[index + 0] / 255.0;*/
 
                     /* Square linear blur. */
+                    /*
                     int blur_width = 5;
                     int blur_width_half = blur_width / 2;
                     int blur_width2 = (blur_width * blur_width);
@@ -334,6 +347,7 @@ int main(int argc, char **argv) {
                     image2[index + 0] /= (blur_width2 * 255.0);
                     image2[index + 1] /= (blur_width2 * 255.0);
                     image2[index + 2] /= (blur_width2 * 255.0);
+                    */
                 }
             }
             glTexImage2D(
@@ -341,9 +355,15 @@ int main(int argc, char **argv) {
                 0, GL_RGB, GL_FLOAT, image2
             );
         }
-        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
 
+        /* Modified. */
+        glUseProgram(program2);
+        glUniform1i(myTextureSampler_location2, 0);
+        glUniform2f(pixD_location2, 1.0 / width, 1.0 / height);
+        glBindVertexArray(vao2);
+        glDrawElements(GL_TRIANGLES, 6, GL_UNSIGNED_INT, 0);
         glBindVertexArray(0);
+
         glfwSwapBuffers(window);
         glfwPollEvents();
         common_fps_print();