Correct Specularity with Texturing

OpenGL OpenGL: Basic Coding
1

Hello friends,

I’m using texture mapping on some of my objects in openGl. I want to display correct specularity with texturing using Blending (GL_BLIND). I’m not sure how that is done and hope you can help.

Ali

2

Define what you mean by “correct specularity” ?

3

If you’re doing old-fashioned, basic, OpenGL (like me), you can show specular highlights on textured objects by doing a simple, two-pass, rendering. It’s discussed on page 296 of the OpenGL SuperBible. I have the 2nd Edition. The page # might be different in later editions. I’ve coded up this technique and find that it works quite well.

4

Need to know what you think “correct” means, but if you mean having specular highlights that have a distinct color and are applied after diffuse texturing, check out GL_SEPARATE_SPECULAR_COLOR (if using fixed-function pipe). If using GLSL, you can emulate this.

5

Hello,

Thanks for the replies.

When I apply texture mapping on my object, the light specularity changes. I’m using a solid sphere as my light source. When applying the texture mapping, the solid sphere (my light) color changes to the same color as that for the texture? I don’t want that to happen.

6

Have you checked the OpenGL SuperBible p. 296 yet?
There’s a one paragraph discussion of your problem and some code that shows you how to fix it.

7

Hi MaxH, Can you tell what chapter I can found this paragraph?

Also, I want to point out that I want to correct specularity using GL_BLEND.

8

In the OpenGL SuperBible Second Edition, it’s in Chapter 8 “Texture Mapping” on page 296.
There’s a section called “Lighting with Textures” with a page titled “Rendering Specular Highlights”.

9

Thanks MaxH. unfortunately the edition I downloaded for Opengl super Bible no longer contain this section.

10

Google ‘OpenGL SuperBible Second Edition’. Looks like you can download it for free.