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start implementing PBR effect

PBR
Evan Hemsley 2020-07-30 17:57:57 -07:00
parent 05bc0341a8
commit f0ffc1746c
5 changed files with 380 additions and 5 deletions
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160
Effects/PBREffect.cs Normal file
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using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Graphics;
namespace Smuggler
{
public struct PBRLight
{
public Vector3 direction;
public Vector3 radiance;
public PBRLight(Vector3 direction, Vector3 radiance)
{
this.direction = direction;
this.radiance = radiance;
}
}
public class PBRLightCollection
{
readonly EffectParameter directionParam;
readonly EffectParameter radianceParam;
private readonly Vector3[] directions = new Vector3[PBREffect.NUM_LIGHTS];
private readonly Vector3[] radiances = new Vector3[PBREffect.NUM_LIGHTS];
public PBRLightCollection(EffectParameter directionParam, EffectParameter radianceParam)
{
this.directionParam = directionParam;
this.radianceParam = radianceParam;
}
public PBRLightCollection(PBRLightCollection other)
{
for (int i = 0; i < PBREffect.NUM_LIGHTS; i++)
{
directions[i] = other.directions[i];
radiances[i] = other.radiances[i];
}
}
public PBRLight this[int index]
{
get
{
return new PBRLight(directions[index], radiances[index]);
}
set
{
directions[index] = value.direction;
radiances[index] = value.radiance;
directionParam.SetValue(directions);
radianceParam.SetValue(radiances);
}
}
}
public class PBREffect : Effect
{
public static readonly int NUM_LIGHTS = 3;
readonly EffectParameter viewProjectionParam;
readonly EffectParameter sceneRotationParam;
readonly EffectParameter eyePositionParam;
readonly EffectParameter specularTextureLevelsParam;
readonly EffectParameter albedoTextureParam;
Matrix world = Matrix.Identity;
Matrix view = Matrix.Identity;
Matrix projection = Matrix.Identity;
Vector3 eyePosition = Vector3.Zero;
int specularTextureLevels = 0;
public Matrix World
{
get { return world; }
set
{
world = value;
sceneRotationParam.SetValue(world);
}
}
public Matrix View
{
get { return view; }
set
{
view = value;
viewProjectionParam.SetValue(projection * view);
eyePositionParam.SetValue(Matrix.Invert(view).Backward);
}
}
public Matrix Projection
{
get { return projection; }
set
{
projection = value;
viewProjectionParam.SetValue(projection * view);
}
}
public PBRLightCollection Lights { get; }
public int SpecularTextureLevels
{
get { return specularTextureLevels; }
set
{
specularTextureLevels = value;
specularTextureLevelsParam.SetValue(specularTextureLevels);
}
}
public Texture2D AlbedoTexture
{
get { return albedoTextureParam.GetValueTexture2D(); }
set { albedoTextureParam.SetValue(value); }
}
public PBREffect(GraphicsDevice graphicsDevice, byte[] effectCode) : base(graphicsDevice, effectCode)
{
viewProjectionParam = Parameters["viewProjectionMatrix"];
sceneRotationParam = Parameters["sceneRotationMatrix"];
eyePositionParam = Parameters["eyePosition"];
specularTextureLevelsParam = Parameters["specularTextureLevels"];
Lights = new PBRLightCollection(Parameters["directions"], Parameters["radiance"]);
}
protected PBREffect(PBREffect cloneSource) : base(cloneSource)
{
viewProjectionParam = Parameters["viewProjectionMatrix"];
sceneRotationParam = Parameters["sceneRotationMatrix"];
eyePositionParam = Parameters["eyePosition"];
specularTextureLevelsParam = Parameters["specularTextureLevels"];
World = cloneSource.World;
View = cloneSource.View;
Projection = cloneSource.Projection;
Lights = new PBRLightCollection(cloneSource.Lights);
}
public override Effect Clone()
{
return new PBREffect(this);
}
// FIXME: do param applications here for performance
protected override void OnApply()
{
base.OnApply();
}
}
}

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Effects/pbr.fx Normal file
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// Physically Based Rendering
// Copyright (c) 2017-2018 Michał Siejak
// Physically Based shading model: Lambetrtian diffuse BRDF + Cook-Torrance microfacet specular BRDF + IBL for ambient.
// This implementation is based on "Real Shading in Unreal Engine 4" SIGGRAPH 2013 course notes by Epic Games.
// See: http://blog.selfshadow.com/publications/s2013-shading-course/karis/s2013_pbs_epic_notes_v2.pdf
static const float PI = 3.141592;
static const float Epsilon = 0.00001;
static const uint NumLights = 3;
// Constant normal incidence Fresnel factor for all dielectrics.
static const float3 Fdielectric = 0.04;
// UNIFORM CONSTANTS
float4x4 viewProjectionMatrix;
float4x4 sceneRotationMatrix;
float3 direction[NumLights];
float3 radiance[NumLights];
float3 eyePosition;
int specularTextureLevels;
struct VertexShaderInput
{
float3 position : POSITION;
float3 normal : NORMAL;
float3 tangent : TANGENT;
float3 binormal : BINORMAL;
float2 texcoord : TEXCOORD;
};
struct PixelShaderInput
{
float4 pixelPosition : SV_POSITION;
float3 position : POSITION1;
float2 texcoord : TEXCOORD0;
float3 T : TEXCOORD1;
float3 B : TEXCOORD2;
float3 N : TEXCOORD3;
};
sampler albedoTexture : register(s0);
sampler normalTexture : register(s1);
sampler metalnessTexture : register(s2);
sampler roughnessTexture : register(s3);
sampler specularTexture : register(s4);
sampler irradianceTexture : register(s5);
sampler specularBRDF_LUT : register(s6);
// GGX/Towbridge-Reitz normal distribution function.
// Uses Disney's reparametrization of alpha = roughness^2.
float ndfGGX(float cosLh, float roughness)
{
float alpha = roughness * roughness;
float alphaSq = alpha * alpha;
float denom = (cosLh * cosLh) * (alphaSq - 1.0) + 1.0;
return alphaSq / (PI * denom * denom);
}
// Single term for separable Schlick-GGX below.
float gaSchlickG1(float cosTheta, float k)
{
return cosTheta / (cosTheta * (1.0 - k) + k);
}
// Schlick-GGX approximation of geometric attenuation function using Smith's method.
float gaSchlickGGX(float cosLi, float cosLo, float roughness)
{
float r = roughness + 1.0;
float k = (r * r) / 8.0; // Epic suggests using this roughness remapping for analytic lights.
return gaSchlickG1(cosLi, k) * gaSchlickG1(cosLo, k);
}
// Shlick's approximation of the Fresnel factor.
float3 fresnelSchlick(float3 F0, float cosTheta)
{
return F0 + (1.0 - F0) * pow(1.0 - cosTheta, 5.0);
}
// Vertex shader
PixelShaderInput main_vs(VertexShaderInput vin)
{
PixelShaderInput vout;
vout.position = mul(sceneRotationMatrix, float4(vin.position, 1.0)).xyz;
vout.texcoord = float2(vin.texcoord.x, 1.0-vin.texcoord.y);
// Pass tangent space basis vectors (for normal mapping).
float3 worldTangent = mul(vin.tangent, (float3x3) sceneRotationMatrix);
vout.T = normalize(worldTangent);
float3 worldBinormal = mul(vin.binormal, (float3x3) sceneRotationMatrix);
vout.B = normalize(worldBinormal);
float3 worldNormal = mul(vin.normal, (float3x3) sceneRotationMatrix);
vout.N = normalize(worldNormal);
float4x4 mvpMatrix = mul(viewProjectionMatrix, sceneRotationMatrix);
vout.pixelPosition = mul(mvpMatrix, float4(vin.position, 1.0));
return vout;
}
// Pixel shader
float4 main_ps(PixelShaderInput pin) : SV_Target0
{
// Sample input textures to get shading model params.
float3 albedo = tex2D(albedoTexture, pin.texcoord).rgb;
float metalness = tex2D(metalnessTexture, pin.texcoord).r;
float roughness = tex2D(roughnessTexture, pin.texcoord).r;
// Outgoing light direction (vector from world-space fragment position to the "eye").
float3 Lo = normalize(eyePosition - pin.position);
// tranpose to transform tangent space => world
float3x3 TBN = transpose(float3x3(normalize(pin.T), normalize(pin.B), normalize(pin.N)));
// Get current fragment's normal and transform to world space.
float3 tangentNormal = normalize(2.0 * tex2D(normalTexture, pin.texcoord).rgb - 1.0);
// world normal
float3 N = normalize(mul(TBN, tangentNormal));
// Angle between surface normal and outgoing light direction.
float cosLo = max(0.0, dot(N, Lo));
// Specular reflection vector.
float3 Lr = 2.0 * cosLo * N - Lo;
// Fresnel reflectance at normal incidence (for metals use albedo color).
float3 F0 = lerp(Fdielectric, albedo, metalness);
// Direct lighting calculation for analytical lights.
float3 directLighting = 0.0;
for(uint i=0; i<NumLights; ++i)
{
float3 Li = -direction[i];
float3 Lradiance = radiance[i];
// Half-vector between Li and Lo.
float3 Lh = normalize(Li + Lo);
// Calculate angles between surface normal and various light vectors.
float cosLi = max(0.0, dot(N, Li));
float cosLh = max(0.0, dot(N, Lh));
// Calculate Fresnel term for direct lighting.
float3 F = fresnelSchlick(F0, max(0.0, dot(Lh, Lo)));
// Calculate normal distribution for specular BRDF.
float D = ndfGGX(cosLh, roughness);
// Calculate geometric attenuation for specular BRDF.
float G = gaSchlickGGX(cosLi, cosLo, roughness);
// Diffuse scattering happens due to light being refracted multiple times by a dielectric medium.
// Metals on the other hand either reflect or absorb energy, so diffuse contribution is always zero.
// To be energy conserving we must scale diffuse BRDF contribution based on Fresnel factor & metalness.
float3 kd = lerp(float3(1, 1, 1) - F, float3(0, 0, 0), metalness);
// Lambert diffuse BRDF.
// We don't scale by 1/PI for lighting & material units to be more convenient.
// See: https://seblagarde.wordpress.com/2012/01/08/pi-or-not-to-pi-in-game-lighting-equation/
float3 diffuseBRDF = kd * albedo;
// Cook-Torrance specular microfacet BRDF.
float3 specularBRDF = (F * D * G) / max(Epsilon, 4.0 * cosLi * cosLo);
// Total contribution for this light.
directLighting += (diffuseBRDF + specularBRDF) * Lradiance * cosLi;
}
// Ambient lighting (IBL).
float3 ambientLighting;
{
// Sample diffuse irradiance at normal direction.
float3 irradiance = tex2D(irradianceTexture, N.xy).rgb;
// Calculate Fresnel term for ambient lighting.
// Since we use pre-filtered cubemap(s) and irradiance is coming from many directions
// use cosLo instead of angle with light's half-vector (cosLh above).
// See: https://seblagarde.wordpress.com/2011/08/17/hello-world/
float3 F = fresnelSchlick(F0, cosLo);
// Get diffuse contribution factor (as with direct lighting).
float3 kd = lerp(1.0 - F, 0.0, metalness);
// Irradiance map contains exitant radiance assuming Lambertian BRDF, no need to scale by 1/PI here either.
float3 diffuseIBL = kd * albedo * irradiance;
// Sample pre-filtered specular reflection environment at correct mipmap level.
float4 levelTexCoord = float4(Lr, roughness * specularTextureLevels);
float3 specularIrradiance = tex2Dlod(specularTexture, levelTexCoord).rgb;
// Split-sum approximation factors for Cook-Torrance specular BRDF.
float2 specularBRDF = tex2D(specularBRDF_LUT, float2(cosLo, roughness)).rg;
// Total specular IBL contribution.
float3 specularIBL = (F0 * specularBRDF.x + specularBRDF.y) * specularIrradiance;
// Total ambient lighting contribution.
ambientLighting = diffuseIBL + specularIBL;
}
// Final fragment color.
return float4(directLighting + ambientLighting, 1.0);
}
technique PBR
{
pass Pass1
{
VertexShader = compile vs_3_0 main_vs();
PixelShader = compile ps_3_0 main_ps();
}
}

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Effects/pbr.fxo Normal file
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4
Importer.cs
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@ -147,9 +147,7 @@ namespace Smuggler
/* TODO: We need a new Effect subclass to support some GLTF features */ /* TODO: We need a new Effect subclass to support some GLTF features */
var effect = new BasicEffect(graphicsDevice); var effect = new PBREffect(graphicsDevice, File.ReadAllBytes("Effects/pbr.fxo"));
effect.EnableDefaultLighting();
effect.PreferPerPixelLighting = true;
return new MeshPart( return new MeshPart(
vertexBuffer, vertexBuffer,

4
MeshPart.cs
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@ -8,10 +8,10 @@ namespace Smuggler
public IndexBuffer IndexBuffer { get; } public IndexBuffer IndexBuffer { get; }
public VertexBuffer VertexBuffer { get; } public VertexBuffer VertexBuffer { get; }
public Triangle[] Triangles { get; } public Triangle[] Triangles { get; }
public BasicEffect Effect { get; } public PBREffect Effect { get; }
public Vector3[] Positions { get; } public Vector3[] Positions { get; }
public MeshPart(VertexBuffer vertexBuffer, IndexBuffer indexBuffer, Vector3[] positions, Triangle[] triangles, BasicEffect effect) public MeshPart(VertexBuffer vertexBuffer, IndexBuffer indexBuffer, Vector3[] positions, Triangle[] triangles, PBREffect effect)
{ {
VertexBuffer = vertexBuffer; VertexBuffer = vertexBuffer;
IndexBuffer = indexBuffer; IndexBuffer = indexBuffer;