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How to get light position in NDC and clip coordinates....

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Almahmudrony

Post subject: How to get light position in NDC and clip coordinates....

Posted: 21.12.2016, 07:34

Joined: 02.12.2016, 12:30
Posts: 23

Hi

i having problem to get world space light position on clip space and Normalized Device Coordinates....
i have tried this to get clip coordinates in shader, vec3(-10,90,100) is the light position on world space....

Code:

vec4 v = projMat * viewMat *vec4(-10,90,100,1);
vec3 lpos = v.xyz/v.w;

but it's not resulting the exact projection location of light on screen :cry:

...

any advice could be highly appreciate....

_________________
~@AlmahmudRony@~

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Irdis

Post subject: Re: How to get light position in NDC and clip coordinates...

Posted: 21.12.2016, 21:19

Joined: 17.11.2009, 17:00
Posts: 205
Location: Russia, Moscow

I don't know exactly how to solve your problem, but take a look how engine calculates the aabb of the screen that is influenced by light source:
https://github.com/horde3d/Horde3D/blob ... gLight.cpp - calcScreenSpaceAABB
Also, check functions in files in utilityLib folder.
For example:

Code:

vec4 calcViewPos( const vec4 pos )
{
   return viewMat * pos;
}

Maybe quad drawing shader can give you a hint:

Code:

[[VS_FSQUAD]]

uniform mat4 projMat;
attribute vec3 vertPos;
varying vec2 texCoords;
            
void main( void )
{
   texCoords = vertPos.xy; 
   gl_Position = projMat * vec4( vertPos, 1 );
}

You can also check this link: https://www.khronos.org/opengl/wiki/Com ... ndow_space

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