Material How to
Let's open one example .material file. es/materials/missing.material would be good to examine. This material is also used when the user specified material is missing. The folder name es means essential and it stores assets for engine internal. You may want to save your material files to data/materials or objects/yourmodel/ folder possibly.
missing.material
<Material>
<ShaderFile>Code/Engine/Renderer/Shaders/Mesh.hlsl</ShaderFile>
<Shaders>VS|PS</Shaders>
<MaterialConstants>
<AmbientColor>0.15, 0.15, 0.15, 1</AmbientColor>
<DiffuseColor_Alpha>1, 0, 0, 1</DiffuseColor_Alpha>
<SpecularColor_Shine>1, 1, 1, 2</SpecularColor_Shine>
<EmissiveColor_Strength>0, 0, 0, 0</EmissiveColor_Strength>
</MaterialConstants>
<Textures>
<Texture slot="0" shader="ps" AddressU="Wrap" AddressV="Wrap">es/textures/missingmaterial.dds</Texture>
</Textures>
<MaterialParameters>
</MaterialParameters>
<ShaderDefines>
</ShaderDefines>
<InputLayout>
<input semantic="POSITION" index="0" format="FLOAT3" slot="0" alignedByteOffset="0" inputSlotClass="VERTEX" stepRate="0"></input>
<input semantic="NORMAL" index="0" format="FLOAT3" slot="1" alignedByteOffset="0" inputSlotClass="VERTEX" stepRate="0"></input>
</InputLayout>
</Material>
A material is defined in XML format. There are not that many elements here. Let's check it out one by one.
-
<ShaderFile>: You define here the .hlsl file you want to use. the path is relative to the execution file. Default engine shaders exist in code/engine/renderer/shaders/ . And you may want to keep your custom shaders in the foler data/shaders. -
<MaterialConstants>: Shader constatns data is defined here. These data can be accessed in the shader using the following constant buffer.
partial text from code/engine/renderer/shaders/constants.h
cbuffer MATERIAL_CONSTANTS
#ifndef CPP
: register (b2)
#endif
{
float4 gAmbientColor;
float4 gDiffuseColor;
float4 gSpecularColor;
float4 gEmissiveColor;
};
-
<Textures>: Defines textures. slot is the register number in the shader. In this example it is using 0 slot. You can access this texture using the following texture object and sampler state object in the shader.
example of code/engine/renderer/shaders/mesh.hlsl
Texture2D gDiffuseTexture : register(t0);
SamplerState gDiffuseSampler : register(s0);
-
2.0f, 0.25, 0.8, 0 2.5f, 1.25, 0.3, 0.5<MaterialParameters>: You can define additional shader constants here. In this example shader, there is no material parameters but if you want to define, write like this.
<param> can be defined up to five. These data can be accessed in the shader through
the following constatns buffer
cbuffer MATERIAL_PARAMETERS
#ifndef CPP
: register (b3)
#endif
{
float4 gMaterialParam[5];
};
-
<ShaderDefines>: You can customize shader behavior using#ifdefcompile preprocessor. for example you define
then you can use the preprocessor
#ifdef ENV_TEXTURE
...
#else
...
#endif
in the shader. (also for PRE_MULTIPLIED_ALPHA)
There is no limitation on numbers of <Define> in the engine.
-
<Shaders>: defines which shader functions the .hlsl file has. if this element is not defined in the material xml, it works same as<Shaders>VS|PS</Shaders>is defined. (VertexShader and PixelShader) -
<InputLayout>: Defines InputLayout which should match the input of vertex shaders. most attributes are defined in DirectX sdk. For the format attributes, you can use FLOAT4, FLOAT3, UBYTE4, FLOAT2, INT4. The engine usually use the different slot number for differenct inputs. For example, POSITION usually bound to slot 0 and NORMAL bound to slot1, and uv to slot2.
Now we are figuring out how to write shaders in the fastbird-engine.
Currently the engine only support DirectX so the extension of the shaders is .hlsl
If you are writing your own mesh shader and you decided its file name to 'mymesh.hlsl', then your shader file should define at least two functions mymesh_VertexShader and mymesh_PixelShader to use it within the material. 'mymesh' is the same with .hlsl file name. and '_VertexShader', '_PixelShader' is predefined strings in the engine.
If you define <Shaders>VS|GS|PS</Shaders> in the material, you also need to define
mymesh_GeometryShader function.
Let's create a simple shader which applys white color on a mesh.
#include "Constants.h"
struct a2v
{
float4 Position : POSITION;
};
struct v2p
{
float4 Position : SV_Position;
};
v2p mymesh_VertexShader( in a2v INPUT )
{
v2p OUTPUT;
OUTPUT.Position = mul( gWorldViewProj, INPUT.Position );
return OUTPUT;
}
float4 mymesh_PixelShader( in v2p INPUT ) : SV_Target
{
// Diffuse Light
return float4(1.0, 1.0, 1.0, 1.0);
}
Constants.h file defines serveral ConstantsBuffers. This include needs for gWorldViewProj variable. The include file location is engine/renderer/shaders/constants.h. Engine usually searches include files at the same folder of the .hlsl exists and if the file is not found, it searches engine/renderer/shaders/ folder.
The a2v struct defines the InputLayout. For this a2v input, InputLayout in the material
is defined like this.
<InputLayout>
<input semantic="POSITION" index="0" format="FLOAT3" slot="0" alignedByteOffset="0" inputSlotClass="VERTEX" stepRate="0"></input>
</InputLayout>
The remain of content is just hlsl codes.
Materials and shaders can be hot reloaded when they are modified in the run-time. If you modify your shader or material, this will be applied to the game running. This feature is essential for fast iteration.
In engine you use IObject::SetMaterial() to set a material to an object. for example,
IMeshObject gMeshObject = 0;
gMeshObject = gEnv->pEngine->GetMeshObject("data/objects/CommandModule/CommandModule.dae"); // using collada file.
if (gMeshObject)
{
gMeshObject->AttachToScene();
gMeshObject->SetMaterial("data/objects/CommandModule/CommandModule.material");
}
But you can also define the material in the dae file in the 3d authoring tool. like the below screen shot.
You can compile and check this material system. Source codes are available at GitHub((https://github.com/fastbird/fastbirdEngine)