Light at objects

[DarkShadow44]

Sorry for this silly post, but lights (with AND without shader) are created for ALL objects, or not ?

How can I set for which objects they work ?

And how can I use more than 8 Lights ? Or only 8 for all/one object ?

How could I give the lights to my shader ?

Sorry but I couldn't figure this out...

[Aleksandar]

Sorry for this silly post, but lights (with AND without shader) are created for ALL objects, or not ?

There is no silly questions!

How can I set for which objects they work ?

For the FFP (without shaders) it can be achieved by using glEnable()/glDisable(). Each particular light-source can be enabled or disabled by glEnable(GL_LIGHTx)/glDisable(GL_LIGHTx). For example use

glEnable(GL_LIGHT1);
//... DrawSomeObjectsWithLight1Effects();
glDisable(GL_LIGHT1);
//... DrawSomeObjectsWithoutLight1Effects();
//... etc

If you want to disable all light sources, than use

glDisable(GL_LIGTING);
//... DrawSomeObjectsWithoutLight();

And how can I use more than 8 Lights ? Or only 8 for all/one object ?

For the FFP only 8! But it is also expensive. Tell me, in what situation you would like to use more than 3 light sources? If there is such need, try to simulate those lights. It is common case to create a texture to simulate lighting effects. It is much cheaper than having lights. Nowadays hardware is strong enough to deal with enormous scenes with multiple lights, but my advice is not to waste the power.

How could I give the lights to my shader ?

It depends on the version of the GLSL. If you are using GLSL up to the version 1.20, then you can get the parameters of the light-sources through build-in uniform variables gl_LightSource[]. The number of light sources is confined to the gl_MaxLights, which is the same value as in FFP, hence 8. In GLSL 1.30 and up, you are free to organize lighting as you like. There are limitations in the number of variables you can have, but you'll probably experience performance degradation before depletion of memory resources for the variables.

Sorry but I couldn't figure this out...

Did I clarify anything, or make things even worse?

[DarkShadow44]

First thanks for your answers, they helped very much ^^

I want ot create one or two lights for a house, and draw this a few times (different houses and each a few times), so light would be nice.

Could I limit lights for the radius of my house ?

And how I set the lights with shaders if I would use more than 8 ? I mean, the shader is executed for every model...

Another question, my lights just can make models(textured) more dark, not brighter, but why ?

But now if the problem that my shader doesn't move my models

gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;

Sorry that doesn't belong here...

[Aleksandar]

Could I limit lights for the radius of my house ?

In FFP this can be done by setting attenuation parameters, but I suggest to relocate lights when moving to another house, keeping the total number of lights to just one or two.

And how I set the lights with shaders if I would use more than 8 ? I mean, the shader is executed for every model...

In GLSL 1.3+ you don't have lights at all! Neither vertices, nor normals... Just attributes! And you can interpret them as you like. So, you can fill the buffer with thousands of coordinates and assume that those are lights' positions and do the lighting calculations.

Another question, my lights just can make models(textured) more dark, not brighter, but why ?

You are probably "modulating" color of the objects with the textures, and the material is too dark, or the amount of light that shade the objects is not enough to make them bright.

But now if the problem that my shader doesn't move my models

gl_Position = gl_ModelViewProjectionMatrix * gl_Vertex;

This part I didn't understand.

[DarkShadow44]

You mean if I move from one house to another to ""turn the light off" ? But what if there are more houses on the screen ?

You mean, in the shader lights are like vectors ?

If I set the light to maximum (1.0, 1.0, 1.0), then my model is as bright as if lightning is turned off


If I use shaders instead of FFP, my model couldn't be translated (I mean moved by "glTranslatef"). All calls to "glTranslatef" and "glRotatef" change nothing...

Could you possibly show your code of loading shaders ??
Because my programm crashes with some shaders at "glBegin" (and my models are "frozen")

[Aleksandar]

You mean if I move from one house to another to ""turn the light off" ? But what if there are more houses on the screen ?

Set the lights and draw one house, than move lights to another position and draw another house etc.

You mean, in the shader lights are like vectors ?

Put whatever you need for lighting into some uniforms and use the data to calculate lighting.

If I set the light to maximum (1.0, 1.0, 1.0), then my model is as bright as if lightning is turned off

That's mean your lighting does not work at all. Post some code to take a look.

If I use shaders instead of FFP, my model couldn't be translated (I mean moved by "glTranslatef"). All calls to "glTranslatef" and "glRotatef" change nothing...

Definitely I need to see the code.

Could you possibly show your code of loading shaders ??
Because my programm crashes with some shaders at "glBegin" (and my models are "frozen")

http://sites.google.com/site/opengltutorialsbyaks/