I know that multi pass rendering is about rendering separate parts of the scene and combining them into on image with blending factors applied , this has been done in rendering graphics. but What is a pass and What are multiple passes in shaders. for example below shader is for diffuse lighting with the 1st light :
Shader "Cg per-vertex diffuse lighting" {
Properties {
_Color ("Diffuse Material Color", Color) = (1,1,1,1)
}
SubShader {
Pass {
Tags { "LightMode" = "ForwardBase" }
// make sure that all uniforms are correctly set
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
uniform float4 _LightColor0;
// color of light source (from "Lighting.cginc")
uniform float4 _Color; // define shader property for shaders
struct vertexInput {
float4 vertex : POSITION;
float3 normal : NORMAL;
};
struct vertexOutput {
float4 pos : SV_POSITION;
float4 col : COLOR;
};
vertexOutput vert(vertexInput input)
{
vertexOutput output;
float4x4 modelMatrix = _Object2World;
float4x4 modelMatrixInverse = _World2Object;
// multiplication with unity_Scale.w is unnecessary
// because we normalize transformed vectors
float3 normalDirection = normalize(float3(
mul(float4(input.normal, 0.0), modelMatrixInverse)));
float3 lightDirection = normalize(
float3(_WorldSpaceLightPos0));
float3 diffuseReflection =
float3(_LightColor0) * float3(_Color)
* max(0.0, dot(normalDirection, lightDirection));
output.col = float4(diffuseReflection, 1.0);
output.pos = mul(UNITY_MATRIX_MVP, input.vertex);
return output;
}
float4 frag(vertexOutput input) : COLOR
{
return input.col;
}
ENDCG
}
}
// The definition of a fallback shader should be commented out
// during development:
// Fallback "Diffuse"
}
And below shader again is for the diffuse lighting with multiple passes and multiple lights.
In the below shader , codes in the both passes are the same , and in the second pass , shader is pointing to _LightColor0 and also in the first pass , shader is using _LightColor0 . So where is multiple lights ? both of passes are pointing to _LightColor0 . I think , both passes are using the first light .
Is it true that a pass has it's private lights array ?
Shader "Cg per-vertex diffuse lighting" {
Properties {
_Color ("Diffuse Material Color", Color) = (1,1,1,1)
}
SubShader {
Pass {
Tags { "LightMode" = "ForwardBase" }
// pass for first light source
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
uniform float4 _LightColor0;
// color of light source (from "Lighting.cginc")
uniform float4 _Color; // define shader property for shaders
struct vertexInput {
float4 vertex : POSITION;
float3 normal : NORMAL;
};
struct vertexOutput {
float4 pos : SV_POSITION;
float4 col : COLOR;
};
vertexOutput vert(vertexInput input)
{
vertexOutput output;
float4x4 modelMatrix = _Object2World;
float4x4 modelMatrixInverse = _World2Object;
// multiplication with unity_Scale.w is unnecessary
// because we normalize transformed vectors
float3 normalDirection = normalize(float3(
mul(float4(input.normal, 0.0), modelMatrixInverse)));
float3 lightDirection = normalize(
float3(_WorldSpaceLightPos0));
float3 diffuseReflection =
float3(_LightColor0) * float3(_Color)
* max(0.0, dot(normalDirection, lightDirection));
output.col = float4(diffuseReflection, 1.0);
output.pos = mul(UNITY_MATRIX_MVP, input.vertex);
return output;
}
float4 frag(vertexOutput input) : COLOR
{
return input.col;
}
ENDCG
}
Pass {
Tags { "LightMode" = "ForwardAdd" }
// pass for additional light sources
Blend One One // additive blending
CGPROGRAM
#pragma vertex vert
#pragma fragment frag
#include "UnityCG.cginc"
uniform float4 _LightColor0;
// color of light source (from "Lighting.cginc")
uniform float4 _Color; // define shader property for shaders
struct vertexInput {
float4 vertex : POSITION;
float3 normal : NORMAL;
};
struct vertexOutput {
float4 pos : SV_POSITION;
float4 col : COLOR;
};
vertexOutput vert(vertexInput input)
{
vertexOutput output;
float4x4 modelMatrix = _Object2World;
float4x4 modelMatrixInverse = _World2Object;
// multiplication with unity_Scale.w is unnecessary
// because we normalize transformed vectors
float3 normalDirection = normalize(float3(
mul(float4(input.normal, 0.0), modelMatrixInverse)));
float3 lightDirection = normalize(
float3(_WorldSpaceLightPos0));
float3 diffuseReflection =
float3(_LightColor0) * float3(_Color)
* max(0.0, dot(normalDirection, lightDirection));
output.col = float4(diffuseReflection, 1.0);
output.pos = mul(UNITY_MATRIX_MVP, input.vertex);
return output;
}
float4 frag(vertexOutput input) : COLOR
{
return input.col;
}
ENDCG
}
}
// The definition of a fallback shader should be commented out
// during development:
// Fallback "Diffuse"
}
UPDATE: this shader works with multiple lights , because I have tested that on cube below with three
lights with three different colors and here is result :
Thanks in advance
