Skydome shader issue

[Tranquility]

I'll keep it simple: I'm trying to make a more "realistic" skydome that doesn't require a texture or something like that. I create the sphere-mesh with some code I found in the source code from Irrlicht's createSkydome.

Then the problems start: I'm not good with shaders.

The theory is this:
I enter a number between 0 and (24*3600) (exclusive).
That number will act as the "skyTime" and I use it calculate a vector that points towards the sun with this:

First I try to find the quadrant the sun is in and use the appropiate formula:

If the time is between 0 and sunriseTime:

Code: Select all

sunPos = vector3df(cos(angle), -sin(angle), 0);

If the time is between sunriseTime and zenithTime:

Code: Select all

sunPos = vector3df(cos(angle), sin(angle), 0);

If the time is between zenithTime and sunsetTime:

Code: Select all

sunPos = vector3df(-cos(angle), sin(angle), 0);

else:

Code: Select all

sunPos = vector3df(-cos(angle), -sin(angle), 0);

Nothing wrong with that (I know it's C++, I just post it to assure you the vectors I use are okay...)

I pass it the shaders with setVertexConstant and try to get the dotproduct of it and the normal.

if the dotproduct is larger the 0.96, draw a sun, or else just black-sky...

here is the vertex shader: (glsl)

Code: Select all

uniform mat4 mWorldViewProj;
uniform mat4 mInvWorld;
uniform mat4 mTransWorld;
uniform vec3 mLightPos; // Sunpos
uniform vec3 mCamPos;

varying float dotP;

void main()
{
	gl_Position = mWorldViewProj * gl_Vertex;
	
	vec4 normal = vec4(gl_Normal, 0.0);
	normal *= mInvWorld;
	normal = normalize(normal);
	
	vec4 worldpos = gl_Vertex * mTransWorld;
	
	vec4 lightVector = worldpos - vec4(mLightPos,1.0);
	lightVector = normalize(lightVector);

	dotP = dot(lightVector, normal);

	gl_TexCoord[0] = gl_MultiTexCoord0;
} 

and here's the fragment-shader:

Code: Select all

varying float dotP;

void main()
{
	if(dotP > 0.96) gl_FragColor = vec4(1.0, 1.0, 1.0, 1.0);
        else gl_FragColor = vec4(0.0, 0.0, 0.0, 1.0);
} 

What am I doing wrong? Everything is just black, sometimes(when I explicitly enter the vector of the sun), the sun just appears, in the wrong direction.[/code]

Edit: Sorry for the double post, didn't found the edit button but here's a screenshot of the working skydome shader, I just can't find the source:

[Tranquility]

FYI: The end-result is going to something like the skydome they use in FarCry2. I made a test-shader (which I lost ) and the result was pretty neat.

[Auradrummer]

Hello Tranquility

I'm making a skydome too, but I'm not drawing the sun or the stars. Your glow effect is really nice! I'll send you mine today, just PM me.