gltut / Tut 03 OpenGLs Moving Triangle / cpuPositionOffset.cpp

Jason McKesson 80244e0 

Jason McKesson da7c819 

Jason McKesson 74c4b9b 
Jason McKesson 80244e0 

Jason McKesson ff914d3 
Jason McKesson 80244e0 

Jason McKesson c689e4d 

Jason McKesson 80244e0 

Jason McKesson c689e4d 
Jason McKesson 80244e0 

Jason McKesson f314aea 

#include <string>
#include <vector>
#include <math.h>
#include <stdio.h>
#include <string.h>
#include <glload/gl_3_3.h>
#include <GL/freeglut.h>
#include "../framework/framework.h"

#define ARRAY_COUNT( array ) (sizeof( array ) / (sizeof( array[0] ) * (sizeof( array ) != sizeof(void*) || sizeof( array[0] ) <= sizeof(void*))))

GLuint theProgram;

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

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

	theProgram = Framework::CreateProgram(shaderList);

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_STATIC_DRAW);
	glBindBuffer(GL_ARRAY_BUFFER, 0);

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

	glGenVertexArrays(1, &vao);

void ComputePositionOffsets(float &fXOffset, float &fYOffset)
	const float fLoopDuration = 5.0f;
	const float fScale = 3.14159f * 2.0f / fLoopDuration;

	float fElapsedTime = glutGet(GLUT_ELAPSED_TIME) / 1000.0f;

	float fCurrTimeThroughLoop = fmodf(fElapsedTime, fLoopDuration);

	fXOffset = cosf(fCurrTimeThroughLoop * fScale) * 0.5f;
	fYOffset = sinf(fCurrTimeThroughLoop * fScale) * 0.5f;

void AdjustVertexData(float fXOffset, float fYOffset)
	std::vector<float> fNewData(ARRAY_COUNT(vertexPositions));
	memcpy(&fNewData[0], vertexPositions, sizeof(vertexPositions));

	for(int iVertex = 0; iVertex < ARRAY_COUNT(vertexPositions); iVertex += 4)
		fNewData[iVertex] += fXOffset;
		fNewData[iVertex + 1] += fYOffset;

	glBindBuffer(GL_ARRAY_BUFFER, positionBufferObject);
	glBufferSubData(GL_ARRAY_BUFFER, 0, sizeof(vertexPositions), &fNewData[0]);
	glBindBuffer(GL_ARRAY_BUFFER, 0);

//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()
	float fXOffset = 0.0f, fYOffset = 0.0f;
	ComputePositionOffsets(fXOffset, fYOffset);
	AdjustVertexData(fXOffset, fYOffset);

	glClearColor(0.0f, 0.0f, 0.0f, 0.0f);


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

	glDrawArrays(GL_TRIANGLES, 0, 3);



//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:

unsigned int defaults(unsigned int displayMode, int &width, int &height) {return displayMode;}