// ==================================================================
// DESTRUCTOR
// ==================================================================
Material::~Material() {
if (hasTextureMap()) {
glDeleteTextures(1,&texture_id);
assert (image != NULL);
delete image;
}
}
// ==================================================================
// OpenGL setup for textures
// ==================================================================
GLuint Material::getTextureID() {
assert (hasTextureMap());
// if this is the first time the texture is being used, we must
// initialize it
if (texture_id == 0) {
glGenTextures(1,&texture_id);
assert (texture_id != 0);
glBindTexture(GL_TEXTURE_2D, texture_id);
// select modulate to mix texture with color for shading
glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_MODULATE);
// or decal to not mix local shading
//glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_DECAL);
// when texture area is small, bilinear filter the closest mipmap
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER,
GL_LINEAR_MIPMAP_NEAREST );
// when texture area is large, bilinear filter the original
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, GL_LINEAR );
// the texture wraps over at the edges (repeat)
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_REPEAT );
glTexParameterf( GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_REPEAT );
// to be most compatible, textures should be square and a power of 2
assert (image->Width() == image->Height());
assert (image->Width() == 256);
// build our texture mipmaps
gluBuild2DMipmaps( GL_TEXTURE_2D, 3, image->Width(), image->Height(),
GL_RGB, GL_UNSIGNED_BYTE, image->getGLPixelData());
}
return texture_id;
}
// ==================================================================
// An average texture color, a hack for use in radiosity
// ==================================================================
void Material::ComputeAverageTextureColor() {
assert (hasTextureMap());
double r = 0;
double g = 0;
double b = 0;
for (int i = 0; i < image->Width(); i++) {
for (int j = 0; j < image->Height(); j++) {
Color c = image->GetPixel(i,j);
r += srgb_to_linear(c.r/255.0);
g += srgb_to_linear(c.g/255.0);
b += srgb_to_linear(c.b/255.0);
}
}
int count = image->Width() * image->Height();
r /= double(count);
g /= double(count);
b /= double(count);
diffuseColor = Vec3f(r,g,b);
}
// ==================================================================
// TEXTURE LOOKUP FOR DIFFUSE COLOR
// ==================================================================
const Vec3f Material::getDiffuseColor(double s, double t) const {
if (!hasTextureMap()) return diffuseColor;
assert (image != NULL);
// simple biliear interpolation on the closest 4 pixels in the texture
double i_ = (s * image->Width());
double j_ = (t * image->Height());
int i1 = int(s * image->Width());
int j1 = int(t * image->Height());
double dx = i_-i1;
double dy = j_-j1;
i1 %= image->Width();
j1 %= image->Height();
if (i1 < 0) i1 += image->Width();
if (j1 < 0) j1 += image->Height();
assert (i1 >= 0 && i1 < image->Width());
assert (j1 >= 0 && j1 < image->Height());
int i2 = i1+1; if (i2 == image->Width()) i2-=1;
int j2 = j1+1; if (j2 == image->Height()) j2-=1;
assert (i2 >= 0 && i2 < image->Width());
assert (j2 >= 0 && j2 < image->Height());
// average the 4 colors
Color c1 = image->GetPixel(i1,j1);
Color c2 = image->GetPixel(i1,j2);
Color c3 = image->GetPixel(i2,j1);
Color c4 = image->GetPixel(i2,j2);
// we assume the texture is stored in sRGB and convert to linear for
// computation. It will be converted back to sRGB before display.
Vec3f c1v(srgb_to_linear(c1.r/255.0),srgb_to_linear(c1.g/255.0),srgb_to_linear(c1.b/255.0));
Vec3f c2v(srgb_to_linear(c2.r/255.0),srgb_to_linear(c2.g/255.0),srgb_to_linear(c2.b/255.0));
Vec3f c3v(srgb_to_linear(c3.r/255.0),srgb_to_linear(c3.g/255.0),srgb_to_linear(c3.b/255.0));
Vec3f c4v(srgb_to_linear(c4.r/255.0),srgb_to_linear(c4.g/255.0),srgb_to_linear(c4.b/255.0));
return c1v*(1-dx)*(1-dy) + c2v*(1-dx)*dy + c3v*dx*(1-dy) + c4v*dx*dy;
}
// ==================================================================
// TEXTURE LOOKUP FOR DIFFUSE COLOR
// ==================================================================
const Vec3f Material::getDiffuseColor(double s, double t) const {
if (!hasTextureMap()) return diffuseColor;
assert (image != NULL);
// this is just using nearest neighbor and could be improved to
// bilinear interpolation, etc.
int i = int(s * image->Width()) % image->Width();
int j = int(t * image->Height()) % image->Height();
if (i < 0) i += image->Width();
if (j < 0) j += image->Height();
assert (i >= 0 && i < image->Width());
assert (j >= 0 && j < image->Height());
Color c = image->GetPixel(i,j);
// we assume the texture is stored in sRGB and convert to linear for
// computation. It will be converted back to sRGB before display.
double r = srgb_to_linear(c.r/255.0);
double g = srgb_to_linear(c.g/255.0);
double b = srgb_to_linear(c.b/255.0);
return Vec3f(r,g,b);
}
