I'm trying to do hardware instancing but I'm hitting some strange performance problem. The average framerate is around 45, but it's extremely choppy.
- Windowed
- SynchronizeWithVerticalRetrace = false
- IsFixedTimeStep = false
- PresentationInterval = PresentInterval.Immediate
The image below shows my measured timing (with Stopwatch). The topmost graph is the time spent in the Draw method and the bottom graph is the time from the end of Draw until the start of Update
The spikes are almost exactly 1 second apart and are always 2,3,4 or 5 times the usual time. The frames immediately following the spike take no time at all. I have checked that it is not the garbage collector.
I'm currently instancing a mesh consisting of 12 triangles and 36 vertices as a triangle list (I know it's not optimal, but it's just for testing) with 1 million instances. If I batch the instancing draw calls into small parts of 250 instances each the problem is alleviated, but cpu usage increases significantly. The run above is at 10000 instance per draw call, which is much easier on the cpu.
If I run the game in fullscreen the bottom graph is almost non-existent, but the same problem occurs now in the Draw method.
Here is a run inside PIX, which makes no sense to me at all. It seems for some frames there is no rendering done...
Any idea, what might be causing this?
EDIT: As requested, the relevant portions of the render code
A CubeBuffer is created and initialized, then filled with cubes. If the amount of cubes is above a certain limit, a new CubeBuffer is created, and so on. Each buffer draws all instances in one call.
Information needed only once is static (vertex, index buffer and vertex declaration; although it makes no difference so far). The texture is 512x512
Draw()
device.Clear(Color.DarkSlateGray);
device.RasterizerState = new RasterizerState() { };
device.BlendState = new BlendState { };
device.DepthStencilState = new DepthStencilState() { DepthBufferEnable = true };
//samplerState=new SamplerState() { AddressU = TextureAddressMode.Mirror, AddressV = TextureAddressMode.Mirror, Filter = TextureFilter.Linear };
device.SamplerStates[0] = samplerState
effect.CurrentTechnique = effect.Techniques["InstancingTexColorLight"];
effect.Parameters["xView"].SetValue(cam.viewMatrix);
effect.Parameters["xProjection"].SetValue(projectionMatrix);
effect.Parameters["xWorld"].SetValue(worldMatrix);
effect.Parameters["cubeTexture"].SetValue(texAtlas);
foreach (EffectPass pass in effect.CurrentTechnique.Passes)
pass.Apply();
foreach (var buf in CubeBuffers)
buf.Draw();
base.Draw(gameTime);
CubeBuffer
[StructLayout(LayoutKind.Sequential)]
struct InstanceInfoOpt9
{
public Matrix World;
public Vector2 Texture;
public Vector4 Light;
};
static VertexBuffer geometryBuffer = null;
static IndexBuffer geometryIndexBuffer = null;
static VertexDeclaration instanceVertexDeclaration = null;
VertexBuffer instanceBuffer = null;
InstanceInfoOpt9[] Buffer = new InstanceInfoOpt9[MaxCubeCount];
Int32 bufferCount=0
Init()
{
if (geometryBuffer == null)
{
geometryBuffer = new VertexBuffer(Device, typeof (VertexPositionTexture), 36, BufferUsage.WriteOnly);
geometryIndexBuffer = new IndexBuffer(Device, typeof (Int32), 36, BufferUsage.WriteOnly);
vertices = new[]{...}
geometryBuffer.SetData(vertices);
indices = new[]{...}
geometryIndexBuffer.SetData(indices);
var instanceStreamElements = new VertexElement[6];
instanceStreamElements[0] = new VertexElement(sizeof (float)*0, VertexElementFormat.Vector4, VertexElementUsage.TextureCoordinate, 1);
instanceStreamElements[1] = new VertexElement(sizeof (float)*4, VertexElementFormat.Vector4, VertexElementUsage.TextureCoordinate, 2);
instanceStreamElements[2] = new VertexElement(sizeof (float)*8, VertexElementFormat.Vector4, VertexElementUsage.TextureCoordinate, 3);
instanceStreamElements[3] = new VertexElement(sizeof (float)*12, VertexElementFormat.Vector4, VertexElementUsage.TextureCoordinate, 4);
instanceStreamElements[4] = new VertexElement(sizeof (float)*16, VertexElementFormat.Vector2, VertexElementUsage.TextureCoordinate, 5);
instanceStreamElements[5] = new VertexElement(sizeof (float)*18, VertexElementFormat.Vector4, VertexElementUsage.TextureCoordinate, 6);
instanceVertexDeclaration = new VertexDeclaration(instanceStreamElements);
}
instanceBuffer = new VertexBuffer(Device, instanceVertexDeclaration, MaxCubeCount, BufferUsage.WriteOnly);
instanceBuffer.SetData(Buffer);
bindings = new[]
{
new VertexBufferBinding(geometryBuffer),
new VertexBufferBinding(instanceBuffer, 0, 1),
};
}
AddRandomCube(Vector3 pos)
{
if(cubes.Count >= MaxCubeCount)
return null;
Vector2 tex = new Vector2(rnd.Next(0, 16), rnd.Next(0, 16))
Vector4 l= new Vector4((float)rnd.Next(), (float)rnd.Next(), (float)rnd.Next(), (float)rnd.Next());
var cube = new InstanceInfoOpt9(Matrix.CreateTranslation(pos),tex, l);
Buffer[bufferCount++] = cube;
return cube;
}
Draw()
{
Device.Indices = geometryIndexBuffer;
Device.SetVertexBuffers(bindings);
Device.DrawInstancedPrimitives(PrimitiveType.TriangleList, 0, 0, 36, 0, 12, bufferCount);
}
Shader
float4x4 xView;
float4x4 xProjection;
float4x4 xWorld;
texture cubeTexture;
sampler TexColorLightSampler = sampler_state
{
texture = <cubeTexture>;
mipfilter = LINEAR;
minfilter = LINEAR;
magfilter = LINEAR;
};
struct InstancingVSTexColorLightInput
{
float4 Position : POSITION0;
float2 TexCoord : TEXCOORD0;
};
struct InstancingVSTexColorLightOutput
{
float4 Position : POSITION0;
float2 TexCoord : TEXCOORD0;
float4 Light : TEXCOORD1;
};
InstancingVSTexColorLightOutput InstancingVSTexColorLight(InstancingVSTexColorLightInput input, float4x4 instanceTransform : TEXCOORD1, float2 instanceTex : TEXCOORD5, float4 instanceLight : TEXCOORD6)
{
float4x4 preViewProjection = mul (xView, xProjection);
float4x4 preWorldViewProjection = mul (xWorld, preViewProjection);
InstancingVSTexColorLightOutput output;
float4 pos = input.Position;
pos = mul(pos, transpose(instanceTransform));
pos = mul(pos, preWorldViewProjection);
output.Position = pos;
output.Light = instanceLight;
output.TexCoord = float2((input.TexCoord.x / 16.0f) + (1.0f / 16.0f * instanceTex.x),
(input.TexCoord.y / 16.0f) + (1.0f / 16.0f * instanceTex.y));
return output;
}
float4 InstancingPSTexColorLight(InstancingVSTexColorLightOutput input) : COLOR0
{
float4 color = tex2D(TexColorLightSampler, input.TexCoord);
color.r = color.r * input.Light.r;
color.g = color.g * input.Light.g;
color.b = color.b * input.Light.b;
color.a = color.a * input.Light.a;
return color;
}
technique InstancingTexColorLight
{
pass Pass0
{
VertexShader = compile vs_3_0 InstancingVSTexColorLight();
PixelShader = compile ps_3_0 InstancingPSTexColorLight();
}
}
