Textures:
Textures are n-dimensional arrays which can contain any information. Usually when talking about textures, we talk about 2D arrays containing color even though there are other types of textures such as height maps, normal maps, specular maps, environment maps and others. Some of them I will be adding to my engine in the later stages. This post is about adding support for 2D textures containing color. Since textures are just arrays, they can be accessed as an array by using co-ordinates. These co-ordinates are called as Texture Co-ordinates or TEXCOORDs or UVs (which is how we will describe them from now on). We get these UVs from mesh authoring programs such as maya. I am programming these UVs to my mesh format and then exporting them as binary. We also specify which texture we want to use for a material in our material file. If there is no texture file specified, we use the default texture which is just white.
return
{
Material =
{
EffectLocation = "Effects/Effect1.Effectbinary",
ConstantType = "float4",
ConstantName = "Color",
ConstantValue = {0,0,0,1},
TextureLocation = "Textures/water.jpg",
},
}
We then add support for textures in our Input layout in C++, vertexLayoutShader and any other shaders that are using textures.
{
auto& positionElement = layoutDescription[2];
positionElement.SemanticName = "TEXCOORD";
positionElement.SemanticIndex = 0; // (Semantics without modifying indices at the end can always use zero)
positionElement.Format = DXGI_FORMAT_R32G32_FLOAT;
positionElement.InputSlot = 0;
positionElement.AlignedByteOffset =offsetof(eae6320::Graphics::VertexFormats::sMesh, u);
positionElement.InputSlotClass = D3D11_INPUT_PER_VERTEX_DATA;
positionElement.InstanceDataStepRate = 0; // (Must be zero for per-vertex data)
}
We also add a sampler state. It specifies how the texture is to be sampled. There can be only one sampler state for the entire application or there can be multiple which can be bound when needed. I am having only one right now which I bind at the start of application.
Once we add support for these in the application code, we have to then sample the texture in the shaders. We perform that using the ‘sample’ instruction in hlsl in which we pass in the texture and the coordinates and get the color at that coordinate. I am performing the sampling in my fragment shader using the function
SampleTexture2d(g_diffuseTexture, g_samplerState, i_textureData)
This expands to i_texture.Sample( i_samplerState, i_uv ).
I then multiply it with the vertex colors to get the final output color.
Meshes with textures on them.
