gltut / Tut 03 OpenGLs Moving Triangle / fragChangeColor.cpp

#include <string>
#include <vector>
#include <math.h>
#include <glloader/gl_3_2_comp.h>
#include <GL/freeglut.h>
#include "../framework/framework.h"

GLuint theProgram;
GLuint positionAttrib;
GLuint elapsedTimeUniform;

void InitializeProgram()
{
	std::vector<GLuint> shaderList;

	shaderList.push_back(Framework::LoadShader(GL_VERTEX_SHADER, "calcOffset.vert"));
	shaderList.push_back(Framework::LoadShader(GL_FRAGMENT_SHADER, "calcColor.frag"));

	theProgram = Framework::CreateProgram(shaderList);

	positionAttrib = glGetAttribLocation(theProgram, "position");
	elapsedTimeUniform = glGetUniformLocation(theProgram, "time");

	GLuint loopDurationUnf = glGetUniformLocation(theProgram, "loopDuration");
	GLuint fragLoopDurUnf = glGetUniformLocation(theProgram, "fragLoopDuration");


	glUseProgram(theProgram);
	glUniform1f(loopDurationUnf, 5.0f);
	glUniform1f(fragLoopDurUnf, 10.0f);
	glUseProgram(0);
}

const float vertexPositions[] = {
	0.25f, 0.25f, 0.0f, 1.0f,
	0.25f, -0.25f, 0.0f, 1.0f,
	-0.25f, -0.25f, 0.0f, 1.0f,
};

GLuint positionBufferObject;
GLuint vao;


void InitializeVertexBuffer()
{
	glGenBuffers(1, &positionBufferObject);

	glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
	glBufferData(GL_ARRAY_BUFFER, sizeof(vertexPositions), vertexPositions, GL_STREAM_DRAW);
	glBindBuffer(GL_ARRAY_BUFFER, 0);
}

//Called after the window and OpenGL are initialized. Called exactly once, before the main loop.
void init()
{
	InitializeProgram();
	InitializeVertexBuffer();

	glGenVertexArrays(1, &vao);
	glBindVertexArray(vao);
}

//Called to update the display.
//You should call glutSwapBuffers after all of your rendering to display what you rendered.
//If you need continuous updates of the screen, call glutPostRedisplay() at the end of the function.
void display()
{
	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);
	glClear(GL_COLOR_BUFFER_BIT);

	glUseProgram(theProgram);

	glUniform1f(elapsedTimeUniform, glutGet(GLUT_ELAPSED_TIME) / 1000.0f);

	glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
	glEnableVertexAttribArray(positionAttrib);
	glVertexAttribPointer(positionAttrib, 4, GL_FLOAT, GL_FALSE, 0, 0);

	glDrawArrays(GL_TRIANGLES, 0, 3);

	glDisableVertexAttribArray(positionAttrib);
	glUseProgram(0);

	glutSwapBuffers();
	glutPostRedisplay();
}

//Called whenever the window is resized. The new window size is given, in pixels.
//This is an opportunity to call glViewport or glScissor to keep up with the change in size.
void reshape (int w, int h)
{
	glViewport(0, 0, (GLsizei) w, (GLsizei) h);
}

//Called whenever a key on the keyboard was pressed.
//The key is given by the ''key'' parameter, which is in ASCII.
//It's often a good idea to have the escape key (ASCII value 27) call glutLeaveMainLoop() to 
//exit the program.
void keyboard(unsigned char key, int x, int y)
{
	switch (key)
	{
	case 27:
		glutLeaveMainLoop();
		break;
	}
}
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