I heard there's a simple way of implementing a sphere glow in a pixel/vertex shader.
How can this be done? I am not using textures or anything. My spheres are entirely rendered with colors.
Shader for sphere glow?
From "old" 9.0b DX SDK:
//// Glow Effect// Copyright (c) Microsoft Corporation. All rights reserved.//// Note: This effect file works with EffectEdit.//string XFile = "tiger.x"; // modelstring BIMG = "lake.bmp"; // Background imageint BCLR = 0xff202080; // background// texturetexture Tex0 < string name = "tiger.bmp"; >;// transformsfloat4x3 WorldView : WORLDVIEW; float4x4 Projection : PROJECTION;// light direction (view space)float3 LightDir < string UIDirectional = "Light Direction"; > = normalize(float3(0.0f, 0.0f, 1.0f));// glow parametersfloat4 GlowColor = float4(0.5f, 0.2f, 0.2f, 1.0f);float4 GlowAmbient = float4(0.2f, 0.2f, 0.0f, 0.0f);float GlowThickness = 0.015f;struct VSTEXTURE_OUTPUT{ float4 Position : POSITION; float4 Diffuse : COLOR; float2 TexCoord : TEXCOORD0;};// draws unskinned object with one texture and one directional light.VSTEXTURE_OUTPUT VSTexture ( float4 Position : POSITION, float3 Normal : NORMAL, float2 TexCoord : TEXCOORD0 ){ VSTEXTURE_OUTPUT Out = (VSTEXTURE_OUTPUT)0; float3 L = -LightDir; // light direction (view space) float3 P = mul(Position, WorldView); // position (view space) float3 N = normalize(mul(Normal, (float3x3)WorldView)); // normal (view space) Out.Position = mul(float4(P, 1), Projection); // projected position Out.Diffuse = max(0, dot(N, L)); // diffuse Out.TexCoord = TexCoord; // texture coordinates return Out; }struct VSGLOW_OUTPUT{ float4 Position : POSITION; float4 Diffuse : COLOR;};// draws a transparent hull of the unskinned object.VSGLOW_OUTPUT VSGlow ( float4 Position : POSITION, float3 Normal : NORMAL ){ VSGLOW_OUTPUT Out = (VSGLOW_OUTPUT)0; float3 N = normalize(mul(Normal, (float3x3)WorldView)); // normal (view space) float3 P = mul(Position, WorldView) + GlowThickness * N; // displaced position (view space) float3 A = float3(0, 0, 1); // glow axis float Power; Power = dot(N, A); Power *= Power; Power -= 1; Power *= Power; // Power = (1 - (N.A)^2)^2 [ = ((N.A)^2 - 1)^2 ] Out.Position = mul(float4(P, 1), Projection); // projected position Out.Diffuse = GlowColor * Power + GlowAmbient; // modulated glow color + glow ambient return Out; }technique TGlowAndTexture{ pass PTexture { // single texture/one directional light shader VertexShader = compile vs_1_1 VSTexture(); PixelShader = NULL; // texture Texture[0] = (Tex0); // sampler states MinFilter[0] = LINEAR; MagFilter[0] = LINEAR; MipFilter[0] = POINT; // set up texture stage states for single texture modulated by diffuse ColorOp[0] = MODULATE; ColorArg1[0] = TEXTURE; ColorArg2[0] = CURRENT; AlphaOp[0] = DISABLE; ColorOp[1] = DISABLE; AlphaOp[1] = DISABLE; } pass PGlow { // glow shader VertexShader = compile vs_1_1 VSGlow(); PixelShader = NULL; // no texture Texture[0] = NULL; // enable alpha blending AlphaBlendEnable = TRUE; SrcBlend = ONE; DestBlend = ONE; // set up texture stage states to use the diffuse color ColorOp[0] = SELECTARG2; ColorArg2[0] = DIFFUSE; AlphaOp[0] = SELECTARG2; AlphaArg2[0] = DIFFUSE; ColorOp[1] = DISABLE; AlphaOp[1] = DISABLE; }}technique TGlowOnly{ pass PGlow { // glow shader VertexShader = compile vs_1_1 VSGlow(); PixelShader = NULL; // no texture Texture[0] = NULL; // enable alpha blending AlphaBlendEnable = TRUE; SrcBlend = ONE; DestBlend = ONE; // set up texture stage states to use the diffuse color ColorOp[0] = SELECTARG2; ColorArg2[0] = DIFFUSE; AlphaOp[0] = SELECTARG2; AlphaArg2[0] = DIFFUSE; ColorOp[1] = DISABLE; AlphaOp[1] = DISABLE; }}
RenderMonkey contains a nice glow effect sample in both HLSL and GLSL. I'm not sure exactly if that's exactly what are you trying to achieve, but it looks cool and seems simple enough. The sample is called "Evil.rfx".
Author
This almost works! The glow can be seen, but there is no transparency. The glow is entirely green with the colors defined as following:
float4 GlowColor = float4(0.0f, 1.0f, 0.0f, 1.0f);
float4 GlowAmbient = float4(0.0f, 1.0f, 0.0f, 0.0f);
It's almost as if it ignores the alpha channel. Any suggestions?
float4 GlowColor = float4(0.0f, 1.0f, 0.0f, 1.0f);
float4 GlowAmbient = float4(0.0f, 1.0f, 0.0f, 0.0f);
It's almost as if it ignores the alpha channel. Any suggestions?
Author
Okay, now there is transparency. I had to add something that wasn't added correctly to the shader.
However, now the results are entirely different. The GlowAmbient color is the one that is in the inner-circle of the glow, and the GlowColor is the color that is in the outer-circle of the glow. Not opposite, as it should be.
Right now, the glow fades from transparent to red. It should fade from red to transparent.
However, now the results are entirely different. The GlowAmbient color is the one that is in the inner-circle of the glow, and the GlowColor is the color that is in the outer-circle of the glow. Not opposite, as it should be.
Right now, the glow fades from transparent to red. It should fade from red to transparent.
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