Lighting shader

Troubleshooting graphics
1

Hi folks!

I’m trying to wrap my head around how to create really basic shader (Phong-Blinn) in JME. How will I get the position of a light in the shader? I’ve specified “LightMode MultiPass” in my MatDef file but the uniform vec4 g_LightPosition is not set correctly. It works fine if I make the light position hardcoded into the shader…

2

what kind of light do you use? directional, point, spot?

3

Right now I’m using a PointLight in world space (5,5,5).

4

ok …it should work, it works for lighting.j3md.



you have to make sure :

  • that you light is added to the scene graph (usually to the root node, or any sub nodes)
  • that you have a vec4 g_LightPosition uniform declared in your shader. (x,y,z are position in world space w is 1/lightRadius)



    if it doesn’t help, please post your material definition and your shader
5

Hmm, now it’s working. I found my problem:



Replace:

[java]vec3 LightDirection = (g_ViewMatrixg_LightPosition.xyz- g_WorldViewMatrix * pos).xyz;[/java]

with:

[java]vec3 LightDirection = (g_ViewMatrixvec4(g_LightPosition.xyz,1.0)- g_WorldViewMatrix * pos).xyz;[/java]



Thanks a lot for the clue. Is this sort of things (like the 1/lightRadius thing) documented somewhere or is it just common knowledge?

1 Like
6

erm…It’s common knowledge among the core team… at least me and Kirril…:stuck_out_tongue:

No, i admit there is a lack of documentation on this.

I’m gonna add this to the jme3 and shaders doc

7

haha, :stuck_out_tongue:



I saw the newly written documentation on the wiki now :slight_smile:

8

btw it made me realize some inconsistencies about how directional lights are handled…