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Simple_VertexShader.c
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/
Simple_VertexShader.c
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// The MIT License (MIT)
//
// Copyright (c) 2013 Dan Ginsburg, Budirijanto Purnomo
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
//
// Book: OpenGL(R) ES 3.0 Programming Guide, 2nd Edition
// Authors: Dan Ginsburg, Budirijanto Purnomo, Dave Shreiner, Aaftab Munshi
// ISBN-10: 0-321-93388-5
// ISBN-13: 978-0-321-93388-1
// Publisher: Addison-Wesley Professional
// URLs: http://www.opengles-book.com
// http://my.safaribooksonline.com/book/animation-and-3d/9780133440133
//
// Simple_VertexShader.c
//
// This is a simple example that draws a rotating cube in perspective
// using a vertex shader to transform the object
//
#include <stdlib.h>
#include "esUtil.h"
typedef struct
{
// Handle to a program object
GLuint programObject;
// Uniform locations
GLint mvpLoc;
// Vertex daata
GLfloat *vertices;
GLuint *indices;
int numIndices;
// Rotation angle
GLfloat angle;
// MVP matrix
ESMatrix mvpMatrix;
} UserData;
///
// Initialize the shader and program object
//
int Init ( ESContext *esContext )
{
UserData *userData = esContext->userData;
const char vShaderStr[] =
"#version 300 es \n"
"uniform mat4 u_mvpMatrix; \n"
"layout(location = 0) in vec4 a_position; \n"
"layout(location = 1) in vec4 a_color; \n"
"out vec4 v_color; \n"
"void main() \n"
"{ \n"
" v_color = a_color; \n"
" gl_Position = u_mvpMatrix * a_position; \n"
"} \n";
const char fShaderStr[] =
"#version 300 es \n"
"precision mediump float; \n"
"in vec4 v_color; \n"
"layout(location = 0) out vec4 outColor; \n"
"void main() \n"
"{ \n"
" outColor = v_color; \n"
"} \n";
// Load the shaders and get a linked program object
userData->programObject = esLoadProgram ( vShaderStr, fShaderStr );
// Get the uniform locations
userData->mvpLoc = glGetUniformLocation ( userData->programObject, "u_mvpMatrix" );
// Generate the vertex data
userData->numIndices = esGenCube ( 1.0, &userData->vertices,
NULL, NULL, &userData->indices );
// Starting rotation angle for the cube
userData->angle = 45.0f;
glClearColor ( 1.0f, 1.0f, 1.0f, 0.0f );
return GL_TRUE;
}
///
// Update MVP matrix based on time
//
void Update ( ESContext *esContext, float deltaTime )
{
UserData *userData = esContext->userData;
ESMatrix perspective;
ESMatrix modelview;
float aspect;
// Compute a rotation angle based on time to rotate the cube
userData->angle += ( deltaTime * 40.0f );
if ( userData->angle >= 360.0f )
{
userData->angle -= 360.0f;
}
// Compute the window aspect ratio
aspect = ( GLfloat ) esContext->width / ( GLfloat ) esContext->height;
// Generate a perspective matrix with a 60 degree FOV
esMatrixLoadIdentity ( &perspective );
esPerspective ( &perspective, 60.0f, aspect, 1.0f, 20.0f );
// Generate a model view matrix to rotate/translate the cube
esMatrixLoadIdentity ( &modelview );
// Translate away from the viewer
esTranslate ( &modelview, 0.0, 0.0, -2.0 );
// Rotate the cube
esRotate ( &modelview, userData->angle, 1.0, 0.0, 1.0 );
// Compute the final MVP by multiplying the
// modevleiw and perspective matrices together
esMatrixMultiply ( &userData->mvpMatrix, &modelview, &perspective );
}
///
// Draw a triangle using the shader pair created in Init()
//
void Draw ( ESContext *esContext )
{
UserData *userData = esContext->userData;
// Set the viewport
glViewport ( 0, 0, esContext->width, esContext->height );
// Clear the color buffer
glClear ( GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT );
// Use the program object
glUseProgram ( userData->programObject );
// Load the vertex position
glVertexAttribPointer ( 0, 3, GL_FLOAT,
GL_FALSE, 3 * sizeof ( GLfloat ), userData->vertices );
glEnableVertexAttribArray ( 0 );
// Set the vertex color to red
glVertexAttrib4f ( 1, 1.0f, 0.0f, 0.0f, 1.0f );
// Load the MVP matrix
glUniformMatrix4fv ( userData->mvpLoc, 1, GL_FALSE, ( GLfloat * ) &userData->mvpMatrix.m[0][0] );
// Draw the cube
glDrawElements ( GL_TRIANGLES, userData->numIndices, GL_UNSIGNED_INT, userData->indices );
}
///
// Cleanup
//
void Shutdown ( ESContext *esContext )
{
UserData *userData = esContext->userData;
if ( userData->vertices != NULL )
{
free ( userData->vertices );
}
if ( userData->indices != NULL )
{
free ( userData->indices );
}
// Delete program object
glDeleteProgram ( userData->programObject );
}
int esMain ( ESContext *esContext )
{
esContext->userData = malloc ( sizeof ( UserData ) );
esCreateWindow ( esContext, "Simple_VertexShader", 320, 240, ES_WINDOW_RGB | ES_WINDOW_DEPTH );
if ( !Init ( esContext ) )
{
return GL_FALSE;
}
esRegisterShutdownFunc ( esContext, Shutdown );
esRegisterUpdateFunc ( esContext, Update );
esRegisterDrawFunc ( esContext, Draw );
return GL_TRUE;
}