OpenGL naughty shaders

opengl/README.md

@@ -29,12 +29,16 @@
         1. [glutBitmapCharacter](bitmap_character.c)
         1. [Animation](animation.c)
     1.  GLFW
-        1. [hello world](glfw_hello_world.c)
-        1. [triangle](glfw_triangle.c)
-        1. [triangles](glfw_triangles.c)
-        1. [shader](glfw_shader.c)
-        1. [transform](glfw_transform.c)
-        1. [animation](glfw_animation.c)
+        1.  [hello world](glfw_hello_world.c)
+        1.  [animation](glfw_animation.c)
+    1.  Retained mode + shaders
+        1.  [triangle](glfw_triangle.c)
+        1.  [color](glfw_color.c)
+        1.  [triangles](glfw_triangles.c)
+        1.  [transform](glfw_transform.c)
+        1.  Naughty
+            1.  [Infinite loop shader](glfw_infinite_loop_shader.c.off)
+            1.  [Memory overflow shader](glfw_memory_overflow_shader.c.off)
     1.  [GLX](glx.c)
     1.  Performance
         1.  [Many triangles](many_triangles.c)

opengl/TODO.md

@@ -45,6 +45,7 @@
 -   https://en.wikipedia.org/wiki/Stencil_buffer
     - http://www.learnopengl.com/#!Advanced-OpenGL/Stencil-testing
 -   shading, glsl
+    - what is the basis for GLSL implementations? GCC, clang, others?
     - pipeline https://www.opengl.org/wiki/Rendering_Pipeline_Overview , great diagram
         - rasterization: determines which pixels are covered by a triangle
     - name is wrong nowadays: shaders can do more things than just shading, including positioning vertexes (e.g. for tesselation) and arbitrary computaiton!
@@ -71,6 +72,10 @@
     - `in`, `out`: http://gamedev.stackexchange.com/questions/29672/in-out-keywords-in-glsl
     - https://www.opengl.org/wiki/Shader
         - there are many types of shaders besides vertex and fragment
+    - get output out of glsl
+        - http://stackoverflow.com/questions/2508818/how-to-debug-a-glsl-shader
+        - http://stackoverflow.com/questions/14086926/get-results-of-gpu-calculations-back-to-the-cpu-program-in-opengl
+        - http://stackoverflow.com/questions/19123239/is-it-possible-to-read-data-from-vertex-shader
 -   motion blur:
     -   http://john-chapman-graphics.blogspot.fr/2013/01/what-is-motion-blur-motion-pictures-are.html
 

opengl/glfw_infinite_loop_shader.c.off

@@ -0,0 +1,82 @@
+/*
+Just for fun.
+
+Blocked my Ubuntu 15.10 with OpenGL 4.5.0 NVIDIA 352.63,
+but I was able to regain control with after a lot of Alt+F4 nd Ctrl+C
+TODO why does it block everything, if it's only in the GPU?
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define GLEW_STATIC
+#include <GL/glew.h>
+
+#include <GLFW/glfw3.h>
+
+#include "common.h"
+
+static const GLuint WIDTH = 800;
+static const GLuint HEIGHT = 600;
+static const GLchar* vertex_shader_source =
+    "#version 330 core\n"
+    "layout (location = 0) in vec3 position;\n"
+    "void main() {\n"
+    "   while(true);\n"
+    "   gl_Position = vec4(position, 1.0);\n"
+    "}\n";
+static const GLchar* fragment_shader_source =
+    "#version 330 core\n"
+    "out vec4 color;\n"
+    "void main() {\n"
+    "   color = vec4(1.0f, 0.0f, 0.0f, 1.0f);\n"
+    "}\n";
+/* Passed as input to the vertex shader. */
+static const GLfloat vertices[] = {
+     0.0f,  0.5f, 0.0f,
+     0.5f, -0.5f, 0.0f,
+    -0.5f, -0.5f, 0.0f,
+};
+
+int main(void) {
+    GLint shader_program;
+
+    glfwInit();
+    GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, __FILE__, NULL, NULL);
+    glfwMakeContextCurrent(window);
+    glewExperimental = GL_TRUE;
+    glewInit();
+    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+    glViewport(0, 0, WIDTH, HEIGHT);
+
+    shader_program = common_get_shader_program(vertex_shader_source, fragment_shader_source);
+
+    GLuint vbo, vao;
+    glGenVertexArrays(1, &vao);
+    glGenBuffers(1, &vbo);
+    glBindVertexArray(vao);
+    glBindBuffer(GL_ARRAY_BUFFER, vbo);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);
+    glEnableVertexAttribArray(0);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+    glBindVertexArray(0);
+
+    while (!glfwWindowShouldClose(window)) {
+        glfwPollEvents();
+
+        /* Render */
+        glClear(GL_COLOR_BUFFER_BIT);
+        glUseProgram(shader_program);
+        glBindVertexArray(vao);
+        glDrawArrays(GL_TRIANGLES, 0, 3);
+        /*glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_INT, 0);*/
+        glBindVertexArray(0);
+
+        glfwSwapBuffers(window);
+    }
+    glDeleteVertexArrays(1, &vao);
+    glDeleteBuffers(1, &vbo);
+    glfwTerminate();
+    return EXIT_SUCCESS;
+}

opengl/glfw_memory_overflow_shader.c.off

@@ -0,0 +1,77 @@
+/*
+Similar effect infinite loop shader :-)
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#define GLEW_STATIC
+#include <GL/glew.h>
+#include <GLFW/glfw3.h>
+
+#include "common.h"
+
+static const GLuint WIDTH = 800;
+static const GLuint HEIGHT = 600;
+static const GLchar* vertex_shader_source =
+    "#version 330 core\n"
+    "layout (location = 0) in vec3 position;\n"
+    "void main() {\n"
+    "   float is[10000000000L];\n"
+    "   gl_Position = vec4(position, is[9999999999L]);\n"
+    "}\n";
+static const GLchar* fragment_shader_source =
+    "#version 330 core\n"
+    "out vec4 color;\n"
+    "void main() {\n"
+    "   color = vec4(1.0f, 0.0f, 0.0f, 1.0f);\n"
+    "}\n";
+/* Passed as input to the vertex shader. */
+static const GLfloat vertices[] = {
+     0.0f,  0.5f, 0.0f,
+     0.5f, -0.5f, 0.0f,
+    -0.5f, -0.5f, 0.0f,
+};
+
+int main(void) {
+    GLint shader_program;
+
+    glfwInit();
+    GLFWwindow* window = glfwCreateWindow(WIDTH, HEIGHT, __FILE__, NULL, NULL);
+    glfwMakeContextCurrent(window);
+    glewExperimental = GL_TRUE;
+    glewInit();
+    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+    glViewport(0, 0, WIDTH, HEIGHT);
+
+    shader_program = common_get_shader_program(vertex_shader_source, fragment_shader_source);
+
+    GLuint vbo, vao;
+    glGenVertexArrays(1, &vao);
+    glGenBuffers(1, &vbo);
+    glBindVertexArray(vao);
+    glBindBuffer(GL_ARRAY_BUFFER, vbo);
+    glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
+    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, (GLvoid*)0);
+    glEnableVertexAttribArray(0);
+    glBindBuffer(GL_ARRAY_BUFFER, 0);
+    glBindVertexArray(0);
+
+    while (!glfwWindowShouldClose(window)) {
+        glfwPollEvents();
+
+        /* Render */
+        glClear(GL_COLOR_BUFFER_BIT);
+        glUseProgram(shader_program);
+        glBindVertexArray(vao);
+        glDrawArrays(GL_TRIANGLES, 0, 3);
+        /*glDrawElements(GL_TRIANGLES, 3, GL_UNSIGNED_INT, 0);*/
+        glBindVertexArray(0);
+
+        glfwSwapBuffers(window);
+    }
+    glDeleteVertexArrays(1, &vao);
+    glDeleteBuffers(1, &vbo);
+    glfwTerminate();
+    return EXIT_SUCCESS;
+}