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Changing the shape of our light |
OK, we’ve got a square light, casting shadows on our scene. How can we make it look more like a real light? A real light shines a round beam of light, so let’s start with that. To determine the pixels that are part of the round beam, we could add some mathematical checks (see Recipe 6-8). That would be OK for a normal light, but for the headlights of a car? This should have 2 beams, so more maths..
In my opinion, a much easier method is to throw in another texture that can be used by our pixel shader:
By looking at the image above I think you get the idea: only the white part will be lit. You can download it by right-clicking on it or by clicking here. We can already add the texture sampler to our HLSL code:
Texture xCarLightTexture;
sampler CarLightSampler = sampler_state { texture = <xCarLightTexture>
; magfilter = LINEAR; minfilter=LINEAR; mipfilter = LINEAR; AddressU = clamp; AddressV = clamp;};
Now we can simply sample the color value of this image, which gives us a value between 0 and 1. We simply need to multiply our final color by this value, so this is the core of our pixel shader:
diffuseLightingFactor = DotProduct(xLightPos, PSIn.Position3D, PSIn.Normal);
diffuseLightingFactor = saturate(diffuseLightingFactor);
diffuseLightingFactor *= xLightPower;
float lightTextureFactor = tex2D(CarLightSampler, ProjectedTexCoords).r;
diffuseLightingFactor *= lightTextureFactor;
That’s it for the HLSL code! In our XNA code, we’re going to load the texture file, so import it into your project and add this variable to our code:
Texture2D carLight;
And this line to our LoadContent method:
carLight = Content.Load<Texture2D>
("carlight");
Now we still need to pass the texture to our effect file. In our DrawScene method, add this line to the list of XNA-to-HLSL parameters we’re passing to the graphics device:
effect.Parameters["xCarLightTexture"].SetValue(carLight);
And this line in the DrawModel method:
currentEffect.Parameters["xCarLightTexture"].SetValue(carLight);
Et voila! That’s all there is to it. You should see the image below:
Click here to go to the forum on this chapter!
Or click on one of the topics on this chapter to go there:
how to move car in
hello
how to move the car in differen...Blank Screen
When i add this section the whole image goes black...
You can also use shaping images with other values than completely white/black. Grey pixels will be lit with less light than white pixels!
The HLSL code:
float4x4 xLightsWorldViewProjection;
float4x4 xWorldViewProjection;
float4x4 xWorld;
bool xSolidBrown;
float3 xLightPos;
float xLightPower;
float xAmbient;
Texture xTexture;
sampler TextureSampler = sampler_state { texture = <xTexture>
; magfilter = LINEAR; minfilter = LINEAR; mipfilter=LINEAR; AddressU = mirror; AddressV = mirror;};
Texture xShadowMap;
sampler ShadowMapSampler = sampler_state { texture = <xShadowMap>
; magfilter = LINEAR; minfilter = LINEAR; mipfilter=LINEAR; AddressU = clamp; AddressV = clamp;};
Texture xCarLightTexture;
sampler CarLightSampler = sampler_state { texture = <xCarLightTexture>
; magfilter = LINEAR; minfilter=LINEAR; mipfilter = LINEAR; AddressU = clamp; AddressV = clamp;};
struct VertexToPixel
{
float4 Position : POSITION;
float2 TexCoords : TEXCOORD0;
float3 Normal : TEXCOORD1;
float3 Position3D : TEXCOORD2;
};
struct PixelToFrame
{
float4 Color : COLOR0;
};
VertexToPixel SimplestVertexShader( float4 inPos : POSITION0, float3 inNormal: NORMAL0, float2 inTexCoords : TEXCOORD0)
{
VertexToPixel Output = (VertexToPixel)0;
Output.Position =mul(inPos, xWorldViewProjection);
Output.TexCoords = inTexCoords;
Output.Normal = normalize(mul(inNormal, (float3x3)xWorld));
Output.Position3D = mul(inPos, xWorld);
return Output;
}
float DotProduct(float3 lightPos, float3 pos3D, float3 normal)
{
float3 lightDir = normalize(pos3D - lightPos);
return dot(-lightDir, normal);
}
PixelToFrame OurFirstPixelShader(VertexToPixel PSIn)
{
PixelToFrame Output = (PixelToFrame)0;
float diffuseLightingFactor = DotProduct(xLightPos, PSIn.Position3D, PSIn.Normal);
diffuseLightingFactor = saturate(diffuseLightingFactor);
diffuseLightingFactor *= xLightPower;
float4 baseColor = tex2D(TextureSampler, PSIn.TexCoords);
if (xSolidBrown == true)
baseColor = float4(0.25f, 0.21f, 0.20f, 1);
Output.Color = baseColor*(diffuseLightingFactor + xAmbient);
return Output;
}
technique Simplest
{
pass Pass0
{
VertexShader = compile vs_2_0 SimplestVertexShader();
PixelShader = compile ps_2_0 OurFirstPixelShader();
}
}
////////////////////////////////////////////////////////////////////////////////////////////////////
struct SMapVertexToPixel
{
float4 Position : POSITION;
float4 Position2D : TEXCOORD0;
};
struct SMapPixelToFrame
{
float4 Color : COLOR0;
};
SMapVertexToPixel ShadowMapVertexShader( float4 inPos : POSITION)
{
SMapVertexToPixel Output = (SMapVertexToPixel)0;
Output.Position = mul(inPos, xLightsWorldViewProjection);
Output.Position2D = Output.Position;
return Output;
}
SMapPixelToFrame ShadowMapPixelShader(SMapVertexToPixel PSIn)
{
SMapPixelToFrame Output = (SMapPixelToFrame)0;
Output.Color = PSIn.Position2D.z/PSIn.Position2D.w;
return Output;
}
technique ShadowMap
{
pass Pass0
{
VertexShader = compile vs_2_0 ShadowMapVertexShader();
PixelShader = compile ps_2_0 ShadowMapPixelShader();
}
}
////////////////////////////////////////////////////////////////////////////////////////////////////
struct SSceneVertexToPixel
{
float4 Position : POSITION;
float4 Pos2DAsSeenByLight : TEXCOORD0;
float2 TexCoords : TEXCOORD1;
float3 Normal : TEXCOORD2;
float3 Position3D : TEXCOORD3;
};
struct SScenePixelToFrame
{
float4 Color : COLOR0;
};
SSceneVertexToPixel ShadowedSceneVertexShader( float4 inPos : POSITION, float2 inTexCoords : TEXCOORD0, float3 inNormal : NORMAL)
{
SSceneVertexToPixel Output = (SSceneVertexToPixel)0;
Output.Position = mul(inPos, xWorldViewProjection);
Output.Pos2DAsSeenByLight = mul(inPos, xLightsWorldViewProjection);
Output.Normal = normalize(mul(inNormal, (float3x3)xWorld));
Output.Position3D = mul(inPos, xWorld);
Output.TexCoords = inTexCoords;
return Output;
}
SScenePixelToFrame ShadowedScenePixelShader(SSceneVertexToPixel PSIn)
{
SScenePixelToFrame Output = (SScenePixelToFrame)0;
float2 ProjectedTexCoords;
ProjectedTexCoords[0] = PSIn.Pos2DAsSeenByLight.x/PSIn.Pos2DAsSeenByLight.w/2.0f +0.5f;
ProjectedTexCoords[1] = -PSIn.Pos2DAsSeenByLight.y/PSIn.Pos2DAsSeenByLight.w/2.0f +0.5f;
float diffuseLightingFactor = 0;
if ((saturate(ProjectedTexCoords).x == ProjectedTexCoords.x) && (saturate(ProjectedTexCoords).y == ProjectedTexCoords.y))
{
float depthStoredInShadowMap = tex2D(ShadowMapSampler, ProjectedTexCoords).r;
float realDistance = PSIn.Pos2DAsSeenByLight.z/PSIn.Pos2DAsSeenByLight.w;
if ((realDistance - 1.0f/100.0f) <= depthStoredInShadowMap)
{
diffuseLightingFactor = DotProduct(xLightPos, PSIn.Position3D, PSIn.Normal);
diffuseLightingFactor = saturate(diffuseLightingFactor);
diffuseLightingFactor *= xLightPower;
float lightTextureFactor = tex2D(CarLightSampler, ProjectedTexCoords).r;
diffuseLightingFactor *= lightTextureFactor;
}
}
float4 baseColor = tex2D(TextureSampler, PSIn.TexCoords);
if (xSolidBrown == true)
baseColor = float4(0.25f, 0.21f, 0.20f, 1);
Output.Color = baseColor*(diffuseLightingFactor + xAmbient);
return Output;
}
technique ShadowedScene
{
pass Pass0
{
VertexShader = compile vs_2_0 ShadowedSceneVertexShader();
PixelShader = compile ps_2_0 ShadowedScenePixelShader();
}
}
And the XNA code:
using System;
using System.Collections.Generic;
using Microsoft.Xna.Framework;
using Microsoft.Xna.Framework.Audio;
using Microsoft.Xna.Framework.Content;
using Microsoft.Xna.Framework.GamerServices;
using Microsoft.Xna.Framework.Graphics;
using Microsoft.Xna.Framework.Input;
using Microsoft.Xna.Framework.Net;
using Microsoft.Xna.Framework.Storage;
namespace XNAseries3
{
public class Game1 : Microsoft.Xna.Framework.Game
{
struct MyOwnVertexFormat
{
private Vector3 position;
private Vector2 texCoord;
private Vector3 normal;
public MyOwnVertexFormat(Vector3 position, Vector2 texCoord, Vector3 normal)
{
this.position = position;
this.texCoord = texCoord;
this.normal = normal;
}
public static VertexElement[] VertexElements =
{
new VertexElement(0, 0, VertexElementFormat.Vector3, VertexElementMethod.Default, VertexElementUsage.Position, 0),
new VertexElement(0, sizeof(float)*3, VertexElementFormat.Vector2, VertexElementMethod.Default, VertexElementUsage.TextureCoordinate, 0),
new VertexElement(0, sizeof(float)*5, VertexElementFormat.Vector3, VertexElementMethod.Default, VertexElementUsage.Normal, 0),
};
public static int SizeInBytes = sizeof(float) * (3 + 2 + 3);
}
GraphicsDeviceManager graphics;
GraphicsDevice device;
Effect effect;
Matrix viewMatrix;
Matrix projectionMatrix;
VertexBuffer vertexBuffer;
VertexDeclaration vertexDeclaration;
Vector3 cameraPos;
Texture2D streetTexture;
Model lamppostModel;
Texture2D[] lamppostTextures;
Model carModel;
Texture2D[] carTextures;
Texture2D carLight;
Vector3 lightPos;
float lightPower;
float ambientPower;
Matrix lightsViewProjectionMatrix;
RenderTarget2D renderTarget;
Texture2D shadowMap;
public Game1()
{
graphics = new GraphicsDeviceManager(this);
Content.RootDirectory = "Content";
}
protected override void Initialize()
{
graphics.PreferredBackBufferWidth = 500;
graphics.PreferredBackBufferHeight = 500;
graphics.IsFullScreen = false;
graphics.ApplyChanges();
Window.Title = "Riemer's XNA Tutorials -- Series 3";
base.Initialize();
}
protected override void LoadContent()
{
device = GraphicsDevice;
effect = Content.Load<Effect>
("OurHLSLfile");
streetTexture = Content.Load<Texture2D>
("streettexture");
carLight = Content.Load<Texture2D>
("carlight");
carModel = LoadModel("racer", out carTextures);
lamppostModel = LoadModel("lamppost", out lamppostTextures);
SetUpVertices();
SetUpCamera();
PresentationParameters pp = device.PresentationParameters;
renderTarget = new RenderTarget2D(device, pp.BackBufferWidth, pp.BackBufferHeight, 1, SurfaceFormat.Single);
}
private Model LoadModel(string assetName, out Texture2D[] textures)
{
Model newModel = Content.Load<Model>
(assetName);
textures = new Texture2D[7];
int i = 0;
foreach (ModelMesh mesh in newModel.Meshes)
foreach (BasicEffect currentEffect in mesh.Effects)
textures[i++] = currentEffect.Texture;
foreach (ModelMesh mesh in newModel.Meshes)
foreach (ModelMeshPart meshPart in mesh.MeshParts)
meshPart.Effect = effect.Clone(device);
return newModel;
}
private void SetUpVertices()
{
MyOwnVertexFormat[] vertices = new MyOwnVertexFormat[18];
vertices[0] = new MyOwnVertexFormat(new Vector3(-20, 0, 10), new Vector2(-0.25f, 25.0f), new Vector3(0, 1, 0));
vertices[1] = new MyOwnVertexFormat(new Vector3(-20, 0, -100), new Vector2(-0.25f, 0.0f), new Vector3(0, 1, 0));
vertices[2] = new MyOwnVertexFormat(new Vector3(2, 0, 10), new Vector2(0.25f, 25.0f), new Vector3(0, 1, 0));
vertices[3] = new MyOwnVertexFormat(new Vector3(2, 0, -100), new Vector2(0.25f, 0.0f), new Vector3(0, 1, 0));
vertices[4] = new MyOwnVertexFormat(new Vector3(2, 0, 10), new Vector2(0.25f, 25.0f), new Vector3(-1, 0, 0));
vertices[5] = new MyOwnVertexFormat(new Vector3(2, 0, -100), new Vector2(0.25f, 0.0f), new Vector3(-1, 0, 0));
vertices[6] = new MyOwnVertexFormat(new Vector3(2, 1, 10), new Vector2(0.375f, 25.0f), new Vector3(-1, 0, 0));
vertices[7] = new MyOwnVertexFormat(new Vector3(2, 1, -100), new Vector2(0.375f, 0.0f), new Vector3(-1, 0, 0));
vertices[8] = new MyOwnVertexFormat(new Vector3(2, 1, 10), new Vector2(0.375f, 25.0f), new Vector3(0, 1, 0));
vertices[9] = new MyOwnVertexFormat(new Vector3(2, 1, -100), new Vector2(0.375f, 0.0f), new Vector3(0, 1, 0));
vertices[10] = new MyOwnVertexFormat(new Vector3(3, 1, 10), new Vector2(0.5f, 25.0f), new Vector3(0, 1, 0));
vertices[11] = new MyOwnVertexFormat(new Vector3(3, 1, -100), new Vector2(0.5f, 0.0f), new Vector3(0, 1, 0));
vertices[12] = new MyOwnVertexFormat(new Vector3(13, 1, 10), new Vector2(0.75f, 25.0f), new Vector3(0, 1, 0));
vertices[13] = new MyOwnVertexFormat(new Vector3(13, 1, -100), new Vector2(0.75f, 0.0f), new Vector3(0, 1, 0));
vertices[14] = new MyOwnVertexFormat(new Vector3(13, 1, 10), new Vector2(0.75f, 25.0f), new Vector3(-1, 0, 0));
vertices[15] = new MyOwnVertexFormat(new Vector3(13, 1, -100), new Vector2(0.75f, 0.0f), new Vector3(-1, 0, 0));
vertices[16] = new MyOwnVertexFormat(new Vector3(13, 21, 10), new Vector2(1.25f, 25.0f), new Vector3(-1, 0, 0));
vertices[17] = new MyOwnVertexFormat(new Vector3(13, 21, -100), new Vector2(1.25f, 0.0f), new Vector3(-1, 0, 0));
vertexBuffer = new VertexBuffer(device, vertices.Length * MyOwnVertexFormat.SizeInBytes, BufferUsage.WriteOnly);
vertexBuffer.SetData(vertices);
vertexDeclaration = new VertexDeclaration(device, MyOwnVertexFormat.VertexElements);
}
private void SetUpCamera()
{
cameraPos = new Vector3(-25, 13, 18);
viewMatrix = Matrix.CreateLookAt(cameraPos, new Vector3(0, 2, -12), new Vector3(0, 1, 0));
projectionMatrix = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver4, device.Viewport.AspectRatio, 5.0f, 100.0f);
}
protected override void UnloadContent()
{
}
protected override void Update(GameTime gameTime)
{
if (GamePad.GetState(PlayerIndex.One).Buttons.Back == ButtonState.Pressed)
this.Exit();
UpdateLightData();
base.Update(gameTime);
}
private void UpdateLightData()
{
ambientPower = 0.5f;
lightPos = new Vector3(-18, 5, -2);
lightPower = 2.0f;
Matrix lightsView = Matrix.CreateLookAt(lightPos, new Vector3(-2, -3, -10), new Vector3(0, 1, 0));
Matrix lightsProjection = Matrix.CreatePerspectiveFieldOfView(MathHelper.PiOver2, 1f, 1f, 100f);
lightsViewProjectionMatrix = lightsView* lightsProjection;
}
protected override void Draw(GameTime gameTime)
{
device.SetRenderTarget(0, renderTarget);
device.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Color.Black, 1.0f, 0);
DrawScene("ShadowMap");
device.SetRenderTarget(0, null);
shadowMap = renderTarget.GetTexture();
device.Clear(ClearOptions.Target | ClearOptions.DepthBuffer, Color.Black, 1.0f, 0);
DrawScene("ShadowedScene");
base.Draw(gameTime);
}
private void DrawScene(string technique)
{
effect.CurrentTechnique = effect.Techniques[technique];
effect.Parameters["xWorldViewProjection"].SetValue(Matrix.Identity * viewMatrix * projectionMatrix);
effect.Parameters["xTexture"].SetValue(streetTexture);
effect.Parameters["xWorld"].SetValue(Matrix.Identity);
effect.Parameters["xLightPos"].SetValue(lightPos);
effect.Parameters["xLightPower"].SetValue(lightPower);
effect.Parameters["xAmbient"].SetValue(ambientPower);
effect.Parameters["xLightsWorldViewProjection"].SetValue(Matrix.Identity * lightsViewProjectionMatrix);
effect.Parameters["xShadowMap"].SetValue(shadowMap);
effect.Parameters["xCarLightTexture"].SetValue(carLight);
effect.Begin();
foreach (EffectPass pass in effect.CurrentTechnique.Passes)
{
pass.Begin();
device.VertexDeclaration = vertexDeclaration;
device.Vertices[0].SetSource(vertexBuffer, 0, MyOwnVertexFormat.SizeInBytes);
device.DrawPrimitives(PrimitiveType.TriangleStrip, 0, 18);
pass.End();
}
effect.End();
Matrix car1Matrix = Matrix.CreateScale(4f) * Matrix.CreateRotationY(MathHelper.Pi) * Matrix.CreateTranslation(-3, 0, -15);
DrawModel(carModel, carTextures, car1Matrix, technique, false);
Matrix car2Matrix = Matrix.CreateScale(4f) * Matrix.CreateRotationY(MathHelper.Pi * 5.0f / 8.0f) * Matrix.CreateTranslation(-28, 0, -1.9f);
DrawModel(carModel, carTextures, car2Matrix, technique, false);
Matrix lamp1Matrix = Matrix.CreateScale(0.05f) * Matrix.CreateTranslation(4.0f, 1, -35);
DrawModel(lamppostModel, lamppostTextures, lamp1Matrix, technique, true);
Matrix lamp2Matrix = Matrix.CreateScale(0.05f) * Matrix.CreateTranslation(4.0f, 1, -5);
DrawModel(lamppostModel, lamppostTextures, lamp2Matrix, technique, true);
}
private void DrawModel(Model model, Texture2D[] textures, Matrix wMatrix, string technique, bool solidBrown)
{
Matrix[] modelTransforms = new Matrix[model.Bones.Count];
model.CopyAbsoluteBoneTransformsTo(modelTransforms);
int i = 0;
foreach (ModelMesh mesh in model.Meshes)
{
foreach (Effect currentEffect in mesh.Effects)
{
Matrix worldMatrix = modelTransforms[mesh.ParentBone.Index] * wMatrix;
currentEffect.CurrentTechnique = currentEffect.Techniques[technique];
currentEffect.Parameters["xWorldViewProjection"].SetValue(worldMatrix * viewMatrix * projectionMatrix);
currentEffect.Parameters["xTexture"].SetValue(textures[i++]);
currentEffect.Parameters["xSolidBrown"].SetValue(solidBrown);
currentEffect.Parameters["xWorld"].SetValue(worldMatrix);
currentEffect.Parameters["xLightPos"].SetValue(lightPos);
currentEffect.Parameters["xLightPower"].SetValue(lightPower);
currentEffect.Parameters["xAmbient"].SetValue(ambientPower);
currentEffect.Parameters["xLightsWorldViewProjection"].SetValue(worldMatrix * lightsViewProjectionMatrix);
currentEffect.Parameters["xShadowMap"].SetValue(shadowMap);
currentEffect.Parameters["xCarLightTexture"].SetValue(carLight);
}
mesh.Draw();
}
}
}
}
- Website design & XNA + DirectX code : Riemer Grootjans -
©2003 - 2008 Riemer Grootjans
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