1. Class 27 more textures environmental textures Color ramps
Reading, writing, and copying pixels
Drawing bitmaps
Bump Maps

2. Wrapping Texture on Curved Surfaces
We want to wrap texture onto a curved surface, such as a beer can or a chess piece.
We assume as before that the object is modeled by a mesh, so it consists of a large number of small flat faces.
Each vertex of the mesh has an associated texture coordinate pair (si, ti).
The main question is finding the proper texture coordinate (s, t) for each vertex of the mesh.

3. OpenGL Reflection Mapping
OpenGL provides a tool to perform approximate environment mapping where the texture is wrapped about a large enclosing sphere:
glTexGenf(GL_S,GL_TEXTURE_GEN_MODE,
GL_SPHERE_MAP);
glTexGenf(GL_T,GL_TEXTURE_GEN_MODE,
glEnable(GL_TEXTURE_GEN_S);
glEnable(GL_TEXTURE_GEN_T);
(Can use GL_CUBE_MAP)

4. shrinkwrapping
Now when a vertex P with its unit normal m is sent down the pipeline, OpenGL calculates a texture coordinate pair (s, t) suitable for indexing into the texture attached to the surrounding sphere.
This is done for each vertex of the face on the object, and the face is drawn as always using interpolated texture coordinates (s, t) for points in between the vertices.

5. There is
GL_CUBE
also if you have 6 textures (views in 6 directions) that you want applied.

6. Example from Guha:
sphereMapping.cpp

7. Another Example
fieldAndSkyOnSphereMJB.cpp
Note culling trick for one texture on inside and one texture on outside.
In general, disble texturing as soon as you draw what you want textured.

8. For texturing:
Use GL_REPLACE for no lighting,
no "bleeding through" of color
Use GL_MODULATE with a white background if you want lighting

9. Color Ramps greyscale : linearly go from (0,0,0) to (1,1,1)
rainbow example, several linear sections – see code.
ColorRamps.c

10. RedbookImage.c from Chapter 8 of the Red book
run and discuss RedbookImage.c
copies from part of the framebuffer to another part of the framebuffer
Does NOT call glutPostRedisplay(), except on reset
Does call flush() to show changes.

11. Reading, Writing, and Copying Pixel data
glReadPixels() - Reads a rectangular array of pixels from the framebuffer and stores the data in processor memory.
glDrawPixels() - Writes a rectangular array of pixels from data kept in processor memory into the framebuffer at the current raster position specified by glRasterPos*().
glCopyPixels() - Copies a rectangular array of pixels from one part of the framebuffer to another.

12. Reading, Writing, and Copying Pixel data
glCopyPixels() command behaves similarly to a call to glReadPixels() followed by a call to glDrawPixels(), but the data is never written into processor memory.

13. void glReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLvoid *pixels);
Reads pixel data from a rectangle in the framebuffer whose lower left coordinate is (x,y) and whose width is width and height is height and stores the data in the array pointed to by pixels.

14. format is the kind of data, for example GL_RGB, but it could also be
void glReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLvoid *pixels);
format is the kind of data, for example GL_RGB, but it could also be
GL_BLUE,
GL_LUMINANCE,
GL_DEPTH_COMPONENT,
...

15. type is the type of the data, eg. GL_UNSIGNED_BYTE
void glReadPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum format, GLenum type, GLvoid *pixels);
type is the type of the data, eg. GL_UNSIGNED_BYTE

16. void glDrawPixels(GLsizei width, GLsizei height, GLenum format, GLenum type, const GLvoid *pixels);
Draws a rectangle of dimension width and height at the current roster position.
format and type as in glReadPixels().
The array pointed to by pixels has the data to be drawn.

17. void glCopyPixels(GLint x, GLint y, GLsizei width, GLsizei height, GLenum buffer);
copies a rectangle with lower left corner (x,y) and dimensions height and width from the buffer to the buffer at the current raster position.

18. Magnifying, Reducing, and Flipping an image
void glPixelZoom(GLfloat zoomx, GLfloat zoomy);

19. void glPixelZoom(GLfloat zoomx, GLfloat zoomy);
by default zoomx and zoomy are both 1.0
If they are both 2 then each image pixel gets drawn to 4 screen pixels.
if (xrp,yrp) is the current raster position, image pixel in row n and column m, will go to the rectangle with corners
(xrp + zoomx * n, yrp + zoomy * m)
and (xrp + zoomx(n+1), yrp + zoomy(m+1))
draws to the pixel if the center of pixel in box.

20. Drawing bitmaps
run RedbookDrawF.c

21. void glBitmap( GLsizei width, GLsizei height, GLfloat xbo, GLfloat ybo, GLfloat xbi, GLfloat ybi, const GLubyte *bitmap);
draws the bitmap pointed to by bitmap.
origin of bitmap at current raster position. xbo and ybo move the origin of the bitmap.
width and height are the dimensions of the bitmap, in pixels.
xbi and ybi are added to the raster position after drawing the bitmap.

22. Sample bitmap

23. starts at lower left corner
GLubyte rasters[24] = {
0xc0, 0x00, 0xc0, 0x00, 0xc0, 0x00, 0xc0, 0x00, 0xc0, 0x00,
0xff, 0x00, 0xff, 0x00, 0xc0, 0x00, 0xc0, 0x00, 0xc0, 0x00,
0xff, 0xc0, 0xff, 0xc0};

24. Bump mapping – procedural textures
bumpmapping.cpp
Change the normals, to give an impression of a texture.