Example 26
This shader program gives a strong shading to points whose normals are close to perpendicular to the viewing direction (which roughly corresponds to the edges of the object, but is view-dependent). Try uncommenting the mag = mag*mag; line in the fragment shader for a faster falloff and a different look! This shader also implements specular lighting to improve the "glassy" effect.
Source Code
main.cpp:
// Alexandri Zavodny
// CSE 40166: Computer Graphics, Fall 2010
// Example: load and execute some simple shaders.
#include <math.h>
#include <GL/glew.h>
#include <GL/glut.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fstream>
#include <iostream>
#include <string>
#include <vector>
using namespace std;
// GLOBAL VARIABLES ////////////////////////////////////////////////////////////
static size_t windowWidth = 640;
static size_t windowHeight = 480;
static float aspectRatio;
GLint leftMouseButton, rightMouseButton; //status of the mouse buttons
int mouseX = 0, mouseY = 0; //last known X and Y of the mouse
float cameraTheta, cameraPhi, cameraRadius; //camera position in spherical coordinates
float x, y, z; //camera position in cartesian coordinates
bool useShader = false;
char *vertexShaderString;
char *fragmentShaderString;
GLuint vertexShaderHandle, fragmentShaderHandle, shaderProgramHandle;
vector<float> vertices;
vector<float> vertexNormals;
vector<int> faceVerts;
vector<int> faceVertNormals;
GLuint objectDisplayList;
// tokenizeString() ////////////////////////////////////////////////////////////
//
// Helper function to break a string into a series of tokens.
//
////////////////////////////////////////////////////////////////////////////////
vector<string> tokenizeString(string input, string delimiters)
{
if(input.size() == 0)
return vector<string>();
vector<string> retVec = vector<string>();
size_t oldR = 0, r = 0;
//strip all delimiter characters from the front and end of the input string.
string strippedInput;
int lowerValidIndex = 0, upperValidIndex = input.size() - 1;
while(lowerValidIndex < input.size() && delimiters.find_first_of(input.at(lowerValidIndex), 0) != string::npos)
lowerValidIndex++;
while(upperValidIndex >= 0 && delimiters.find_first_of(input.at(upperValidIndex), 0) != string::npos)
upperValidIndex--;
//if the lowest valid index is higher than the highest valid index, they're all delimiters! return nothing.
if(lowerValidIndex >= input.size() || upperValidIndex < 0 || lowerValidIndex >= upperValidIndex)
return vector<string>();
//remove the delimiters from the beginning and end of the string, if any.
strippedInput = input.substr(lowerValidIndex, upperValidIndex-lowerValidIndex+1);
//search for each instance of a delimiter character, and create a new token spanning
//from the last valid character up to the delimiter character.
while((r = strippedInput.find_first_of(delimiters, oldR)) != string::npos)
{
if(oldR != r) //but watch out for multiple consecutive delimiters!
retVec.push_back(strippedInput.substr(oldR, r-oldR));
oldR = r+1;
}
if(r != 0)
retVec.push_back(strippedInput.substr(oldR, r-oldR));
return retVec;
}
// loadOBJ() ///////////////////////////////////////////////////////////////////
//
// Simple function to load an OBJ file. Doesn't support anything fancy; just
// vertices, normals, and faces.
//
////////////////////////////////////////////////////////////////////////////////
void loadOBJ(string filename)
{
string line;
ifstream in(filename.c_str());
while(getline(in, line))
{
vector<string> tokens = tokenizeString(line, " /");
if(tokens.size() < 4) continue;
if(!tokens.at(0).compare("v"))
{
vertices.push_back(atof(tokens.at(1).c_str()));
vertices.push_back(atof(tokens.at(2).c_str()));
vertices.push_back(atof(tokens.at(3).c_str()));
} else if(!tokens.at(0).compare("vn")) {
vertexNormals.push_back(atof(tokens.at(1).c_str()));
vertexNormals.push_back(atof(tokens.at(2).c_str()));
vertexNormals.push_back(atof(tokens.at(3).c_str()));
} else if(!tokens.at(0).compare("f")) {
faceVerts.push_back(atoi(tokens.at(1).c_str()));
faceVerts.push_back(atoi(tokens.at(3).c_str()));
faceVerts.push_back(atoi(tokens.at(5).c_str()));
faceVertNormals.push_back(atoi(tokens.at(2).c_str()));
faceVertNormals.push_back(atoi(tokens.at(4).c_str()));
faceVertNormals.push_back(atoi(tokens.at(6).c_str()));
}
}
printf("We have %d vertices, %d vertex normals, and %d faces.\n",
vertices.size()/3, vertexNormals.size()/3, faceVerts.size()/3);
in.close();
}
// createOBJDisplayList() //////////////////////////////////////////////////////
//
// Simple helper function to create a display list for the loaded OBJ file.
//
////////////////////////////////////////////////////////////////////////////////
void createOBJDisplayList()
{
objectDisplayList = glGenLists(1);
glNewList(objectDisplayList, GL_COMPILE);
glColor3f(0.8,0.8,0.8);
glBegin(GL_TRIANGLES);
for(int i = 0; i < faceVerts.size()/3; i++)
{
int idx1 = faceVerts.at(i*3+0)-1;
int idx2 = faceVerts.at(i*3+1)-1;
int idx3 = faceVerts.at(i*3+2)-1;
int nIdx1 = faceVertNormals.at(i*3+0)-1;
int nIdx2 = faceVertNormals.at(i*3+1)-1;
int nIdx3 = faceVertNormals.at(i*3+2)-1;
glNormal3f(vertexNormals.at(nIdx1*3+0), vertexNormals.at(nIdx1*3+1), vertexNormals.at(nIdx1*3+2));
glVertex3f(vertices.at(idx1*3+0), vertices.at(idx1*3+1), vertices.at(idx1*3+2));
glNormal3f(vertexNormals.at(nIdx2*3+0), vertexNormals.at(nIdx2*3+1), vertexNormals.at(nIdx2*3+2));
glVertex3f(vertices.at(idx2*3+0), vertices.at(idx2*3+1), vertices.at(idx2*3+2));
glNormal3f(vertexNormals.at(nIdx3*3+0), vertexNormals.at(nIdx3*3+1), vertexNormals.at(nIdx3*3+2));
glVertex3f(vertices.at(idx3*3+0), vertices.at(idx3*3+1), vertices.at(idx3*3+2));
}
glEnd();
glEndList();
}
// readTextFile() //////////////////////////////////////////////////////////////
//
// Reads in a text file as a single string. Used to aid in shader loading.
//
////////////////////////////////////////////////////////////////////////////////
void readTextFile(string filename, char* &output)
{
string buf = string("");
string line;
ifstream in(filename.c_str());
while(getline(in, line))
buf += line + "\n";
output = new char[buf.length()+1];
strncpy(output, buf.c_str(), buf.length());
output[buf.length()] = '\0';
in.close();
}
// recomputeOrientation() //////////////////////////////////////////////////////
//
// This function updates the camera's position in cartesian coordinates based
// on its position in spherical coordinates. Should be called every time
// cameraTheta, cameraPhi, or cameraRadius is updated.
//
////////////////////////////////////////////////////////////////////////////////
void recomputeOrientation()
{
x = cameraRadius * sinf(cameraTheta)*sinf(cameraPhi);
z = cameraRadius * -cosf(cameraTheta)*sinf(cameraPhi);
y = cameraRadius * -cosf(cameraPhi);
glutPostRedisplay();
}
// resizeWindow() //////////////////////////////////////////////////////////////
//
// GLUT callback for window resizing. Resets GL_PROJECTION matrix and viewport.
//
////////////////////////////////////////////////////////////////////////////////
void resizeWindow(int w, int h)
{
aspectRatio = w / (float)h;
windowWidth = w;
windowHeight = h;
//update the viewport to fill the window
glViewport(0, 0, w, h);
//update the projection matrix with the new window properties
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluPerspective(45.0,aspectRatio,0.1,100000);
}
// mouseCallback() /////////////////////////////////////////////////////////////
//
// GLUT callback for mouse clicks. We save the state of the mouse button
// when this is called so that we can check the status of the mouse
// buttons inside the motion callback (whether they are up or down).
//
////////////////////////////////////////////////////////////////////////////////
void mouseCallback(int button, int state, int thisX, int thisY)
{
//update the left and right mouse button states, if applicable
if(button == GLUT_LEFT_BUTTON)
leftMouseButton = state;
else if(button == GLUT_RIGHT_BUTTON)
rightMouseButton = state;
//and update the last seen X and Y coordinates of the mouse
mouseX = thisX;
mouseY = thisY;
}
// mouseMotion() ///////////////////////////////////////////////////////////////
//
// GLUT callback for mouse movement. We update cameraPhi, cameraTheta, and/or
// cameraRadius based on how much the user has moved the mouse in the
// X or Y directions (in screen space) and whether they have held down
// the left or right mouse buttons. If the user hasn't held down any
// buttons, the function just updates the last seen mouse X and Y coords.
//
////////////////////////////////////////////////////////////////////////////////
void mouseMotion(int x, int y)
{
if(leftMouseButton == GLUT_DOWN)
{
cameraTheta += (x - mouseX)*0.005;
cameraPhi += (y - mouseY)*0.005;
// make sure that phi stays within the range (0, M_PI)
if(cameraPhi <= 0)
cameraPhi = 0+0.001;
if(cameraPhi >= M_PI)
cameraPhi = M_PI-0.001;
recomputeOrientation(); //update camera (x,y,z) based on (radius,theta,phi)
} else if(rightMouseButton == GLUT_DOWN) {
double totalChangeSq = (x - mouseX) + (y - mouseY);
cameraRadius += totalChangeSq*0.01;
//limit the camera radius to some reasonable values so the user can't get lost
if(cameraRadius < 2.0)
cameraRadius = 2.0;
if(cameraRadius > 10.0)
cameraRadius = 10.0;
recomputeOrientation(); //update camera (x,y,z) based on (radius,theta,phi)
}
mouseX = x;
mouseY = y;
}
// initScene() /////////////////////////////////////////////////////////////////
//
// A basic scene initialization function; should be called once after the
// OpenGL context has been created. Doesn't need to be called further.
//
////////////////////////////////////////////////////////////////////////////////
void initScene()
{
glEnable(GL_DEPTH_TEST);
float lightCol[4] = { 1.0f, 1.0f, 1.0f, 1.0f};
float ambientCol[4] = {0.1, 0.1, 0.1, 1.0};
glLightfv(GL_LIGHT0,GL_DIFFUSE,lightCol);
glLightfv(GL_LIGHT0, GL_AMBIENT, ambientCol);
glEnable(GL_LIGHTING);
glEnable(GL_LIGHT0);
glShadeModel(GL_SMOOTH);
}
// renderScene() ///////////////////////////////////////////////////////////////
//
// GLUT callback for scene rendering. Sets up the modelview matrix, renders
// a teapot to the back buffer, and switches the back buffer with the
// front buffer (what the user sees).
//
////////////////////////////////////////////////////////////////////////////////
void renderScene(void)
{
//update the modelview matrix based on the camera's position
glMatrixMode(GL_MODELVIEW); //make sure we aren't changing the projection matrix!
glLoadIdentity();
gluLookAt(x, y, z, //camera is located at (x,y,z)
0, 0, 0, //camera is looking at (0,0,0)
0.0f,1.0f,0.0f); //up vector is (0,1,0) (positive Y)
float lPosition[4] = { 10, 10, 10, 1 };
glLightfv(GL_LIGHT0,GL_POSITION,lPosition);
//clear the render buffer
glClear(GL_COLOR_BUFFER_BIT | GL_DEPTH_BUFFER_BIT);
glEnable(GL_BLEND);
glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
glEnable(GL_CULL_FACE);
glCullFace(GL_BACK);
//draw some boxes flying around the model! why? i don't know!
glPushMatrix();
glRotatef(glutGet(GLUT_ELAPSED_TIME)/50.0f,0,1,0);
glUseProgram(0);
glPushMatrix();
glTranslatef(2,0,2);
glutSolidCube(0.5f);
glPopMatrix();
glPushMatrix();
glTranslatef(-2,0,2);
glutSolidCube(0.5f);
glPopMatrix();
glPushMatrix();
glTranslatef(-2, 0, -2);
glutSolidCube(0.5f);
glPopMatrix();
glPushMatrix();
glTranslatef(2,0,-2);
glutSolidCube(0.5f);
glPopMatrix();
glPopMatrix();
//draw the model
glUseProgram(shaderProgramHandle);
glEnable(GL_NORMALIZE);
glPushMatrix();
glTranslatef(0.0f,-1.5f,0.0f);
glScalef(0.001,0.001,0.001);
glCallList(objectDisplayList);
glPopMatrix();
//push the back buffer to the screen
glutSwapBuffers();
}
// normalKeys() ////////////////////////////////////////////////////////////////
//
// GLUT keyboard callback.
//
////////////////////////////////////////////////////////////////////////////////
void normalKeys(unsigned char key, int x, int y)
{
if(key == 'q' || key == 'Q')
exit(0);
if(key == 'c' || key == 'C')
useShader = !useShader;
}
// setupShaders() //////////////////////////////////////////////////////////////
//
// A simple helper subrouting that performs the necessary steps to enable shaders
// and bind them appropriately. Note because we're using global variables,
// everything is relatively hard-coded, including filenames, and none of
// the information are passed to the function as parameters.
//
////////////////////////////////////////////////////////////////////////////////
void setupShaders()
{
readTextFile("angleOfIncidence.vert", vertexShaderString);
readTextFile("angleOfIncidence.frag", fragmentShaderString);
vertexShaderHandle = glCreateShader(GL_VERTEX_SHADER);
fragmentShaderHandle = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(vertexShaderHandle, 1, (const char**)&vertexShaderString, NULL);
glShaderSource(fragmentShaderHandle, 1, (const char**)&fragmentShaderString, NULL);
//free up that memory cause we're awesome programmers.
delete [] vertexShaderString;
delete [] fragmentShaderString;
glCompileShader(vertexShaderHandle);
glCompileShader(fragmentShaderHandle);
shaderProgramHandle = glCreateProgram();
glAttachShader(shaderProgramHandle, vertexShaderHandle);
glAttachShader(shaderProgramHandle, fragmentShaderHandle);
glLinkProgram(shaderProgramHandle);
glUseProgram(shaderProgramHandle);
}
void timer(int val)
{
glutTimerFunc(1000.0 / 24.0, timer, 0);
glutPostRedisplay();
}
// main() //////////////////////////////////////////////////////////////////////
//
// Program entry point. Does not process command line arguments.
//
////////////////////////////////////////////////////////////////////////////////
int main(int argc, char **argv)
{
//create a double-buffered GLUT window at (50,50) with predefined windowsize
glutInit(&argc, argv);
glutInitDisplayMode(GLUT_DEPTH | GLUT_DOUBLE | GLUT_RGBA);
//glutInitDisplayString("depth>=12 double rgba samples>2");
glutInitWindowPosition(50,50);
glutInitWindowSize(windowWidth,windowHeight);
glutCreateWindow("oooh shiny");
glewInit();
if(!glewIsSupported("GL_VERSION_2_0"))
{
fprintf(stderr, "Error! OpenGL 2.0 not supported on this machine.\n");
exit(1);
}
//give the camera a 'pretty' starting point!
cameraRadius = 7.0f;
cameraTheta = 2.80;
cameraPhi = 2.0;
recomputeOrientation();
//register callback functions...
glutKeyboardFunc(normalKeys);
glutDisplayFunc(renderScene);
//glutIdleFunc(renderScene);
glutReshapeFunc(resizeWindow);
glutMouseFunc(mouseCallback);
glutMotionFunc(mouseMotion);
//do some basic OpenGL setup
initScene();
setupShaders();
loadOBJ("venus.obj");
createOBJDisplayList();
glutTimerFunc(1000.0 / 24.0, timer, 0);
//and enter the GLUT loop, never to exit.
glutMainLoop();
return(0);
}