• Modify the initial color of the point to create texture effects.
• Projected texture - Project each 3D point Q to a 2D point P in an pixmap, also called the texture.
• Assign to Q the color of P before applying any light algorithm.
• Can also interpolate between the original color of the point and the color of the texture.
• Question: how to tile the texture image on the 3D object smoothly.
• Texture mapping - Same as before, but perturb the texture map by a function. Simulates rough looking surface.
• Solid texture - Compute the texture map by an analytical function. Wood, stone, marble, checker board, complex fabric patterns, etc.

• Textures can be in 1D, 2D, or 3D.
• Each of them is stored in an array of bytes of size 3*nr of pixels.
• For the 1D texture, size=length.
• For the 2D texture, size=width*height.
• For the 3D texture, size=width*height*depth.
• Each dimension must be a power of 2.

• The bitmap file must have both width and height equal to a power of 2.
• The BMP file is binary, and has the following structure:
• Bitmap File Header – specify that the file is a bitmap
• Bitmap Info – contains the width and height
• Pixel data - 3b per pixel - bgr (rgb upside down)

• Enable - disable the texture:

glEnable(GL_TEXTURE_2D); //1D, 3D
glDisable(GL_TEXTURE_2D);
• Create the texture out of the array of points:

glTexImage2D(GL_TEXTURE_2D,0,3,width,height,0,GL_RGB,GL_UNSIGNED_BYTE,buffer);
• Parameters: target, level, components, width, height, border, format, type, *pixels.

• Defines the interaction of the texture with current light and color.
• GL_MODULATE - light properties apply to the texture.
• GL_DECAL - light and color don't affect the texture.
• GL_BLEND - mixes the currently active

glTexEnvf(GL_TEXTURE_ENV, GL_TEXTURE_ENV_MODE, GL_BLEND);

• 2 types of filters: minification, for polygons smaller than the image, and magnification, for polygons larger than the image.

glTexParameterf(GL_TEXTURE_2D,GL_TEXTURE_WRAP_S,GL_CLAMP);
• Filters: GL_NEAREST, GL_LINEAR, GL_LINEAR_MIPMAP_NEAREST, a combination of each of them and MIPMAP
• Mipmaped textures: based on several images, can chose the one that is appropriate for the level of detail.

• Associates a particular location in the texture with a vertex.
• For a 2D texture, the coordinates are denoted by s and t. Both of them are between 0.0 and 1.0.

glTexCoord2d(0.0, 1.0);
• The glTexCoord2d must be used before the vertex it applies to.

Snapshots from this program:

GL_DECAL option for the texture mode, marble bitmap.

GL_DECAL option for the texture mode, pattern bitmap.

GL_MODULATE option for the texture mode, marble bitmap.

GL_BLEND option for the texture mode, applied to the marble bitmap with a previously defined purple color.

GL_BLEND option for the texture mode, applied to the tiles bitmap with a previously defined purple color.

Another example with the texture applied to a quadric object: texture_quadric.cc