AnimationProf. Aaron LantermanSchool of Electrical and Computer EngineeringGeorgia Institute of Technology2Typical keyframed animations• Standing• Running• Kneeling• Ducking• Attacking• Passing on, ceasing to be, expiring and going tomeet maker, pushing up the daisies, kicking thebucket, shuffling off mortal coil, running down thecurtain, joining the invisible choir, becoming anex-parrotFrom Fernando & Kilgard, “The Cg Tutorial,” 2003, p. 1553Basic keyframing (fragment shader)void C6E3v_keyFrame(float3 positionA : POSITION, float3 positionB : TEXCOORD1, float4 color : COLOR, float2 texCoord : TEXCOORD0, out float4 oPosition : POSITION, out float2 oTexCoord : TEXCOORD0, out float4 oColor : COLOR, uniform float keyFrameBlend, uniform float4x4 modelViewProj){ float3 position = lerp(positionA, positionB, keyFrameBlend); oPosition = mul(modelViewProj, float4(position, 1)); oTexCoord = texCoord; oColor = color;}From Fernando & Kilgard, “The Cg Tutorial,” 2003, p. 1594A Light structurestruct Light { float3 eyePosition; // In object space float3 lightPosition; // In object space float4 lightColor; float specularExponent; float ambient;};From Fernando & Kilgard, “The Cg Tutorial,” 2003, p. 1615Keyframing with lighting (vertex shader)void C6E4v_litKeyFrame(float3 positionA : POSITION, float3 normalA : NORMAL, float3 positionB : TEXCOORD1, float3 normalB : TEXCOORD2, float2 texCoord : TEXCOORD0, out float4 oPosition : POSITION, out float2 oTexCoord : TEXCOORD0, out float4 color : COLOR, uniform float keyFrameBlend, uniform Light light, uniform float4x4 modelViewProj){ float3 position = lerp(positionA, poitionB, keyFrameBlend); float3 blendNormal = lerp(normalA, normalB, keyFrameBlend); float3 normal = normalize(blendNormal); oPosition = mul(modelViewProj, float4(position, 1)); oTexCoord = texCoord; color = computeLighting(light, position, normal);}From Fernando & Kilgard, “The Cg Tutorial,” 2003, p. 1626Compute lightingfloat4 computeLighting(Light light, float3 position, // In object space float3 normal) // In object space{ float3 lightDirection = light.lightPosition - position; float3 lightDirNorm = normalize(lightDirection); float3 eyeDirection = light.eyePosition - position; float3 eyeDirNorm = normalize(eyeDirection); float3 halfAngle = normalize(lightDirNorm + eyeDirNorm); float diffuse = max(0,dot(lightDirNorm, normal)); float specular = pow(max(0,dot(halfAngle, normal)), light.specularExponent); return light.lightColor * (light.ambient + diffuse + specular);}From Fernando & Kilgard, “The Cg Tutorial,” 2003, p. 1617Skinning, part 1 (vertex shader)void C6E5v_skin4m(float3 position : POSITION, float3 normal : NORMAL, float2 texCoord : TEXCOORD0, float4 weight : TEXCOORD1, float4 matrixIndex : TEXCOORD2, out float4 oPosition : POSITION, out float2 oTexCoord : TEXCOORD0, out float4 color : COLOR, uniform Light light, uniform float4 boneMatrix[72], // 24 matrices uniform float4x4 modelViewProj){ …From Fernando & Kilgard, “The Cg Tutorial,” 2003, p. 1668Skinning, part 2 (vertex shader) … float3 netPosition = 0, netNormal = 0; for (int i=0; i<4; i++) { float index = matrixIndex[i]; float3x4 model = float3x4(boneMatrix[index+0], boneMatrix[index+1], boneMatrix[index+2]); float3 bonePosition = mul(model, float4(position, 1)); // Assume no scaling in matrix, just rotate & translate float3x3 rotate = float3x3(model[0].xyz, model[1].xyz, model[2].xyz); float3 boneNormal = mul(rotate, normal); netPosition += weight[i] * bonePosition; netNormal += weight[i] * boneNormal; } …From Fernando & Kilgard, “The Cg Tutorial,” 2003, p. 1669Skinning, part 3 (vertex shader) … netNormal = normalize(netNormal); oPosition = mul(modelViewProj, float4(netPosition, 1)); oTexCoord = texCoord; color = computeLighting(light, netPosition, netNormal);}From Fernando & Kilgard, “The Cg Tutorial,” 2003, p.
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