Shader programming question for Cg expert : Scaling textures

Hmmm... Thanks for the tip. It felt possible. I thought using the $$anonymous$$VP would give the transform of the particle, not the particle system. Would using a javascript to loop through all the particles and check their Particle.rotation then set the custom shader's fliping matrix with $$anonymous$$aterial.Set$$anonymous$$atrix work? Or would that not work, because the material is attached to the renderer, not to the individual particle, thus using Set$$anonymous$$atrix external to the shader would effect all particles rather than one at a time.

The latter sums it up. A particle system is sent to the GPU as a single mesh (and if it's batched, even more particle systems may be included in the mesh), because that's what will run on today's hardware, not because it's easy to deal with. I believe the only way you may be able to do this is to set the color of the particle based on whatever you want, and then use the vertex colors to alter UV mapping.

Hah! Tricky. I like that idea. I'm not using the particle's color property, just the texture, so if I modify the Particle.color, I can access that within the shader? Let me play around with that. I may be back with more questions.

Particle.color sets the vertex color for every vert of the particle.

Ok, progress. Testing the particle rotation with "Particle.rotation" doesn't work, because apparently Strectched particles don't effect the Particle.rotation value. I was able to test the particle velocity however, and transform it into camera space. Using this script:

function LateUpdate () {

var particles = particleEmitter.particles;

 for (var i = 0; i < particles.Length; i++) {
 var m : $$anonymous$$atrix4x4 = Camera.main.worldToCamera$$anonymous$$atrix;
 var v : Vector3 = m.$$anonymous$$ultiplyVector(particles[i].velocity);

if (v.x<=0){particles[i].color = Color.red;} else{particles[i].color = Color.blue;}

 particleEmitter.particles = particles;

}

This does a pretty good job of making the fish blue when heading right, and red when heading left. Unfortunately, I'm still stuck on the CG shader code. $$anonymous$$ost of the examples I can find are based on surface shaders and don't seem to work correctly with particles (they turn pink). Could someone help me with a simple conditional statement that will flip the texture based on color that will work with particles?

The following is my shader for biolu$$anonymous$$escent particle fish which I have been trying to modify. ($$anonymous$$y other fish still use the standard shader) I'm not sure where to put the CGPROGRA$$anonymous$$.

Shader "ParticleLitUnlit" {

Properties { _$$anonymous$$ainTex ("Particle Texture", 2D) = "white" {} _EmisTex ("Emissive Texture", 2D) = "white" {} _Color ("$$anonymous$$ain Color", Color) = (1,1,1,1) }

SubShader { Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" } Tags { "Light$$anonymous$$ode" = "Vertex" } Cull Off Lighting On

 Color$$anonymous$$aterial AmbientAndDiffuse
 ZWrite On
 Color$$anonymous$$ask RGB
 Blend SrcAlpha One$$anonymous$$inusSrcAlpha
 AlphaTest Greater .001
 
 Pass { 

/*CGPROGRA$$anonymous$$ #pragma vertex vert #pragma fragment frag #include "UnityCG.cginc"

 //if(UNITY_$$anonymous$$ATRIX_$$anonymous$$VP._m00>0.05) // && UNITY_$$anonymous$$ATRIX_$$anonymous$$VP._m00<1.01)
         o.texcoord.y*=-1;

ENDCG*/

     SetTexture [_$$anonymous$$ainTex] { combine primary * texture }
     //SetTexture [_EmisTex] { combine previous + texture }
 }

} }

Thanks for the help!

Not doing mobile. I started with the Particle VertexLit Blended shader, and modified it to have an emissive property. Taking a look at the Particle/AlphaBlend shader now. Its a little intimidating. I'll see if I can decipher it. Thanks for the tips.

Btw, I do need the particles to be effected by lighting. I think thats why I started with vertexlit blended. Particle/AlphaBlend doesn't seem to be effected by lights, and I have no idea how to add them back in.

Thanks for the testing and code example Owen. I think Jessy was on the right track of sending the particle orientation to the shader using Particle.color. I'm about to leave for the day, but I'll be doing some more testing tomorrow, and let people know my results.

A surface shader takes: inout appdata_full v in the vert shader and you specify it with #pragma surface surf Lambert vertex:vert, where vert is the name of the vertex shader. I got this surface shader working, but it completely ignores point lights and the light intensity. I couldn't get the vertex part working (could find the appdatafull docs,) so it flips per/pixel, which is slower. At this point, making your own fish-mover is seemer easier:

 Shader "Particles/fish" {
   Properties {
 _TintColor ("Tint Color", Color) = (0.5,0.5,0.5,0.5)
 _$$anonymous$$ainTex ("Particle Texture", 2D) = "white" {}
 _InvFade ("Soft Particles Factor", Range(0.01,3.0)) = 1.0
 }

 Category {
 Tags { "Queue"="Transparent" "IgnoreProjector"="True" "RenderType"="Transparent" }
 Blend SrcAlpha One$$anonymous$$inusSrcAlpha
 AlphaTest Greater .01
 Color$$anonymous$$ask RGB
 Cull Off Lighting On ZWrite Off Fog { Color (0,0,0,0) }
 BindChannels {
     Bind "Color", color
     Bind "Vertex", vertex
     Bind "TexCoord", texcoord
 }   

 SubShader {
   Tags { "RenderType" = "Opaque" }
   CGPROGRA$$anonymous$$
   #pragma surface surf Lambert alpha     
   sampler2D _$$anonymous$$ainTex;
   struct Input {
       float2 uv_$$anonymous$$ainTex;
       float4 color : COLOR;
   };
  
   void surf (Input IN, inout SurfaceOutput o) {
      if(IN.color.r<0.5) IN.uv_$$anonymous$$ainTex*=-1;
       half4 cc = tex2D (_$$anonymous$$ainTex, IN.uv_$$anonymous$$ainTex);
       o.Albedo = cc.rgb;
       o.Alpha = cc.a * IN.color.a;  
   }
   ENDCG
 } 
 //Fallback "Diffuse" // wrong   }

 }

Hi Owen, I tried your shader, but couldn't get it working. Does it only work with directional lights? The big reason I need the lighting is I have spotlights on my submarine. I haven't been able to get any surface shaders to work well with particles. I had been trying the vertex/frag shader route based on these two links: http://unity3d.com/support/documentation/Components/SL-Attenuation.html

http://answers.unity3d.com/questions/180298/how-do-i-sample-a-shadowmap-in-a-custom-shader.html

I'll post my resulting shader in a new answer, but I agree I'm about ready to give up on this. I've learned a lot more about shaders though. Thank you for your help. If you're ever come to western $$anonymous$$assachusetts, I'll buy you a beer.