Mikmacer at 19:26, 10 August 2008

2008-08-10T19:26:52Z

Mikmacer at 19:26, 10 August 2008

2008-08-10T19:26:31Z

Mikmacer at 19:25, 10 August 2008

2008-08-10T19:25:37Z

Mikmacer: New page: {| border="0" | {{ContentBlock|width=800|color=white |content={{!!}} == Overview == '''What is the Fresnel shader?''' This shader combine reflection and refraction that depends on the ...

2008-08-10T19:14:40Z

New page: {| border="0" | {{ContentBlock|width=800|color=white |content={{!!}} == Overview == '''What is the Fresnel shader?''' This shader combine reflection and refraction that depends on the ...

New page

{| border="0"
| {{ContentBlock|width=800|color=white
|content={{!!}}

== Overview ==
'''What is the Fresnel shader?'''
This shader combine reflection and refraction that depends on the viewing angle.

'''What is refraction?'''
According to the "OpenGL Shading Language Book", refraction is the blending of light as it passes trough a boundary between surfaces with different optical densities.

'''Requirements:'''<BR/>
- A cube map texture.

== The shader ==
Can be put in the ATTRIBPASS or AMBIENT context to be used with the examples pipelines in the Horde3D SDK 1.0 beta.

'''Vertex shader:'''
In the vertex shader, you can freely change the indices of refraction or the degree of reflectivity to change de final result.

{{CppSourceCode|
description= Fresnel - Vertex Shader|
code=
<source lang="cpp" line="1">
const float Eta = 0.67; // Ratio of indices of refraction (air -> glass)
const float FresnelPower = 10.0; // Controls degree of reflectivity at grazing angles

const float F = ((1.0 - Eta) * (1.0 - Eta)) / ((1.0 + Eta) * (1.0 + Eta));

varying vec3 Reflect;
varying vec3 Refract;
varying float Ratio;

attribute vec3 normal;

uniform vec3 viewer;

void main( void )
{
vec4 worldPosition = calcWorldPos( gl_Vertex );
vec3 ecPosition3 = worldPosition.xyz - viewer;//viewer - worldPosition.xyz;

vec3 i = normalize(ecPosition3);
vec3 n = normalize( calcWorldVec(normal) );

Ratio = F + (1.0 - F) * pow((1.0 - dot(-i, n)), FresnelPower);
//Ratio = 1.0 - Ratio; // Add this line if your cube map is not based on the right side

Refract = refract(i, n, Eta);
Refract = vec3(gl_TextureMatrix[0] * vec4(Refract, 1.0));

Reflect = reflect(i, n);
Reflect = vec3(gl_TextureMatrix[0] * vec4(Reflect, 1.0));

gl_Position = gl_ModelViewProjectionMatrix * worldPosition;
}
</source>}}

'''Fragment shader:'''

{{CppSourceCode|
description= Fresnel - Vertex Shader|
code=
<source lang="cpp" line="1">
varying vec3 Reflect;
varying vec3 Refract;
varying float Ratio;

uniform samplerCube tex0;

void main(void)
{
vec3 refractColor = vec3 (textureCube(tex0, Refract));
vec3 reflectColor = vec3 (textureCube(tex0, Reflect));

vec3 color = mix(refractColor, reflectColor, Ratio);

gl_FragColor = vec4(color, 1.0);
}
</source>}}

== How to use it ==
You must create a material in wich the shader is defined as the fresnel shader. Then, you must add the Texture unit 0 with a cube map type texture.

== Example Result ==

To do.

== Pictures ==
http://img143.imageshack.us/img143/2072/fresnel3ej6.png

== To-Do List for this Article ==
- Better explanation <br />
- An example

}}
| valign="top" | {{Extension_Summary
|name = Technique - Fresnel
|screenshot =
|description = Using reflection and refraction
|version = 1.0
|horde3dversion = 1.0 beta
|released = 2008-08-10
|author = [http://www.horde3d.org/forums/memberlist.php?mode=viewprofile&u=154 Mikmacer]|
}}
|}
[[category: Technique]]

@@ Line 39: / Line 39: @@
+{
      vec4 worldPosition = calcWorldPos( gl_Vertex );
-     vec3 ecPosition3  = worldPosition.xyz - viewer;//viewer - worldPosition.xyz;
+     vec3 ecPosition3  = worldPosition.xyz - viewer;
      vec3 i = normalize(ecPosition3);

@@ Line 62: / Line 62: @@
 {{CppSourceCode|
-description=  Fresnel - Vertex Shader|
+description=  Fresnel - Fragment Shader|
 code=
 <source lang="cpp" line="1">

@@ Line 87: / Line 87: @@
 == Example Result ==
-To do.
+http://www.horde3d.org/forums/download/file.php?id=52
 == Pictures ==
@@ Line 94: / Line 94: @@
 == To-Do List for this Article ==
 - Better explanation <br />
 }}

Shading Technique - Fresnel - Revision history

Mikmacer at 19:26, 10 August 2008

Mikmacer at 19:26, 10 August 2008

Mikmacer at 19:25, 10 August 2008

Mikmacer: New page: {| border="0" | {{ContentBlock|width=800|color=white |content={{!!}} == Overview == '''What is the Fresnel shader?''' This shader combine reflection and refraction that depends on the ...