tutorial12.cpp

/*

	Copyright 2010 Etay Meiri

    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program.  If not, see <http://www.gnu.org/licenses/>.

    Tutorial 12 - Perspective Projection
*/


#include <stdio.h>
#include <string.h>
#include <assert.h>
#include <math.h>
#include <GL/glew.h>
#include <GL/freeglut.h>

#include "ogldev_util.h"
#include "ogldev_pipeline.h"

#define WINDOW_WIDTH 1024
#define WINDOW_HEIGHT 768

GLuint VBO;
GLuint IBO;
GLuint gWorldLocation;
PersProjInfo gPersProjInfo;

const char* pVSFileName = "shader.vs";
const char* pFSFileName = "shader.fs";


static void RenderSceneCB()
{
    glClear(GL_COLOR_BUFFER_BIT);

    static float Scale = 0.0f;

    Scale += 0.1f;

    Pipeline p;
    p.Rotate(0.0f, Scale, 0.0f);
    p.WorldPos(0.0f, 0.0f, 5.0f);
    p.SetPerspectiveProj(gPersProjInfo);

    glUniformMatrix4fv(gWorldLocation, 1, GL_TRUE, (const GLfloat*)p.GetWPTrans());

    glEnableVertexAttribArray(0);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glVertexAttribPointer(0, 3, GL_FLOAT, GL_FALSE, 0, 0);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IBO);

    glDrawElements(GL_TRIANGLES, 12, GL_UNSIGNED_INT, 0);

    glDisableVertexAttribArray(0);

    glutSwapBuffers();
}


static void InitializeGlutCallbacks()
{
    glutDisplayFunc(RenderSceneCB);
    glutIdleFunc(RenderSceneCB);
}

static void CreateVertexBuffer()
{
    Vector3f Vertices[4];
    Vertices[0] = Vector3f(-1.0f, -1.0f, 0.5773f);
    Vertices[1] = Vector3f(0.0f, -1.0f, -1.15475f);
    Vertices[2] = Vector3f(1.0f, -1.0f, 0.5773f);
    Vertices[3] = Vector3f(0.0f, 1.0f, 0.0f);

    glGenBuffers(1, &VBO);
    glBindBuffer(GL_ARRAY_BUFFER, VBO);
    glBufferData(GL_ARRAY_BUFFER, sizeof(Vertices), Vertices, GL_STATIC_DRAW);
}

static void CreateIndexBuffer()
{
    unsigned int Indices[] = { 0, 3, 1,
                               1, 3, 2,
                               2, 3, 0,
                               0, 1, 2 };

    glGenBuffers(1, &IBO);
    glBindBuffer(GL_ELEMENT_ARRAY_BUFFER, IBO);
    glBufferData(GL_ELEMENT_ARRAY_BUFFER, sizeof(Indices), Indices, GL_STATIC_DRAW);
}

static void AddShader(GLuint ShaderProgram, const char* pShaderText, GLenum ShaderType)
{
    GLuint ShaderObj = glCreateShader(ShaderType);

    if (ShaderObj == 0) {
        fprintf(stderr, "Error creating shader type %d\n", ShaderType);
        exit(1);
    }

    const GLchar* p[1];
    p[0] = pShaderText;
    GLint Lengths[1];
    Lengths[0]= strlen(pShaderText);
    glShaderSource(ShaderObj, 1, p, Lengths);
    glCompileShader(ShaderObj);
    GLint success;
    glGetShaderiv(ShaderObj, GL_COMPILE_STATUS, &success);
    if (!success) {
        GLchar InfoLog[1024];
        glGetShaderInfoLog(ShaderObj, 1024, NULL, InfoLog);
        fprintf(stderr, "Error compiling shader type %d: '%s'\n", ShaderType, InfoLog);
        exit(1);
    }

    glAttachShader(ShaderProgram, ShaderObj);
}

static void CompileShaders()
{
    GLuint ShaderProgram = glCreateProgram();

    if (ShaderProgram == 0) {
        fprintf(stderr, "Error creating shader program\n");
        exit(1);
    }
	
    string vs, fs;

    if (!ReadFile(pVSFileName, vs)) {
        exit(1);
    };

    if (!ReadFile(pFSFileName, fs)) {
        exit(1);
    };

    AddShader(ShaderProgram, vs.c_str(), GL_VERTEX_SHADER);
    AddShader(ShaderProgram, fs.c_str(), GL_FRAGMENT_SHADER);

    GLint Success = 0;
    GLchar ErrorLog[1024] = { 0 };
    glBindAttribLocation(ShaderProgram, 0, "Position");
    glLinkProgram(ShaderProgram);
    glGetProgramiv(ShaderProgram, GL_LINK_STATUS, &Success);
	if (Success == 0) {
		glGetProgramInfoLog(ShaderProgram, sizeof(ErrorLog), NULL, ErrorLog);
		fprintf(stderr, "Error linking shader program: '%s'\n", ErrorLog);
        exit(1);
	}

    glValidateProgram(ShaderProgram);
    glGetProgramiv(ShaderProgram, GL_VALIDATE_STATUS, &Success);
    if (!Success) {
        glGetProgramInfoLog(ShaderProgram, sizeof(ErrorLog), NULL, ErrorLog);
        fprintf(stderr, "Invalid shader program: '%s'\n", ErrorLog);
        exit(1);
    }

    glUseProgram(ShaderProgram);

    gWorldLocation = glGetUniformLocation(ShaderProgram, "gWorld");
    assert(gWorldLocation != 0xFFFFFFFF);
}

int main(int argc, char** argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_DOUBLE|GLUT_RGBA);
    glutInitWindowSize(WINDOW_WIDTH, WINDOW_HEIGHT);
    glutInitWindowPosition(100, 100);
    glutCreateWindow("Tutorial 12");

    InitializeGlutCallbacks();

    // Must be done after glut is initialized!
    GLenum res = glewInit();
    if (res != GLEW_OK) {
      fprintf(stderr, "Error: '%s'\n", glewGetErrorString(res));
      return 1;
    }
    
    glClearColor(0.0f, 0.0f, 0.0f, 0.0f);

    CreateVertexBuffer();
    CreateIndexBuffer();

    CompileShaders();

    gPersProjInfo.FOV = 30.0f;
    gPersProjInfo.Height = WINDOW_HEIGHT;
    gPersProjInfo.Width = WINDOW_WIDTH;
    gPersProjInfo.zNear = 1.0f;
    gPersProjInfo.zFar = 100.0f;
	                
    glutMainLoop();

    return 0;
}