koobas.hobune.stream
Lerping in a shader
I'm trying to create a basic shader that just lerps between two base colors. The lerping works if I adjust the blend knob, but now I want to make it so it flashes by it's self.
I was able to find examples that used a shader along side a script that passes the blend value, but I want to do it all in the shader.
I though I programmed it correctly, but it doesn't appear to be fading between the two colors.
My shader:
Shader "Game/Solid/SolidFlash"
{
Properties
{
_Blend("Blend", Range(0, 1)) = 0.5
_BlendSpeed("Blend Speed", Range(0, 50)) = 0.5
_Color("Main Color", Color) = (1, 1, 1, 1)
_Color2("Flash Color", Color) = (1, 1, 1, 1)
_MainTex("Texture 1", 2D) = "white" {}
}
SubShader
{
Tags{ "Queue" = "Transparent" "RenderType" = "Transparent" }
LOD 300
Pass
{
SetTexture[_MainTex]
}
CGPROGRAM
#pragma surface surf Lambert
sampler2D _MainTex;
fixed4 _Color;
fixed4 _Color2;
float _Blend;
float _BlendSpeed;
int forward = 1;
struct Input
{
float2 uv_MainTex;
float2 uv_Texture2;
};
void surf(Input IN, inout SurfaceOutput o)
{
if (forward == 1) {
_Blend += unity_DeltaTime.x / _BlendSpeed;
if (_Blend >= 1)
forward = 0;
}
else {
_Blend -= unity_DeltaTime.x / _BlendSpeed;
if (_Blend <= 0)
forward = 1;
}
fixed4 tex = tex2D(_MainTex, IN.uv_MainTex);
o.Albedo = (lerp(_Color, _Color2, _Blend)+ tex * tex.a); // lerp(t1, t2, _Blend);
}
ENDCG
}
FallBack "Diffuse"
}
While valid syntax, using if statements in a shader is considered a big no-no that should be absolutely avoided if possible. The GPU is a pipeline processor that can run a fixed set of instructions against a massive number of fragments very efficiently. But as soon as you implement branching logic, that pipeline must be rebuilt - defeating the parallelism at which GPUs excel.
A better solution would be to perform calculations in a C# script on the CPU and just pass that value to the shader, as in the examples you said you've already found.
Something like this @lancer ?
void surf(Input IN, inout SurfaceOutput o)
{
_Blend = (1+_SinTime.w) / 2;
fixed4 tex = tex2D(_MainTex, IN.uv_MainTex);
o.Albedo = lerp(_Color, _Color2, _Blend) * tex;
}
