What is the best practice to render sprites in DirectX 11?

Question

I am currently trying to get used to the DirectX API and I am wondering what is the usual approach to render a sprite in DirectX 11 (e.g. for a tetris clone).

Is there a simmilar interface as ID3DX10Sprite, and if not, which would be the usual method to draw sprites in DirectX 11?

Edit: Here is the HLSL code that worked for me (the computation of the projection coordinate could be done better):

struct SpriteData
{
    float2 position;
    float2 size;
    float4 color;
};

struct VSOut
{
    float4 position : SV_POSITION;
    float4 color : COLOR;
};

cbuffer ScreenSize : register(b0)
{
    float2 screenSize;
    float2 padding; // cbuffer must have at least 16 bytes
}

StructuredBuffer<SpriteData> spriteData : register(t0);

float2 GetVertexPosition(uint VID)
{
    [branch] switch(VID)
    {
        case 0:
            return float2(0, 0); 
        case 1:
            return float2(1, 0); 
        case 2:
            return float2(0, 1); 
        default:
            return float2(1, 1);
    }
}

float4 ComputePosition(float2 positionInScreenSpace, float2 size, float2 vertexPosition)
{
    float2 origin = float2(-1, 1);
    float2 vertexPositionInScreenSpace = positionInScreenSpace + (size * vertexPosition);

    return float4(origin.x + (vertexPositionInScreenSpace.x / (screenSize.x / 2)), origin.y - (vertexPositionInScreenSpace.y / (screenSize.y / 2)), 1, 1);
}

VSOut VShader(uint VID : SV_VertexID, uint SIID : SV_InstanceID)
{
    VSOut output;

    output.color = spriteData[SIID].color;
    output.position = ComputePosition(spriteData[SIID].position, spriteData[SIID].size, GetVertexPosition(VID));

    return output;
}

float4 PShader(float4 position : SV_POSITION, float4 color : COLOR) : SV_TARGET
{
    return color;
}

Chloris

Answer 1

No there isn't an equivalent. Usual method would be to draw a triangle strip forming a quad.

You could make use of instancing, so you just have to update a buffer with sprite data (x, y screen position in pixels, id of the texture to fetch in a texture array, scaling, rotation, layer, etc) and use shaders for rendering all sprites in one single draw call.

Here's some HLSL tidbits off the top of my head:

//--------------------------------------------------------------------------------------
// Shader code for Sprite Rendering
//--------------------------------------------------------------------------------------

struct Sprite {
    float2 position; // x, y world position
    float rotation;
    float scaling;

    float layer; // if you have multiple layers of sprites (e.g. background sprites)
    uint textureId;
};

StructuredBuffer<Sprite> SpritesRO : register( t0 );
Texture2DArray<float4> TextureSlices : register (t1);

cbuffer cbRenderConstants : register( b0 )
{
    matrix g_mViewProjection;
    // other constants
};

struct VSSpriteOut
{
    float3 position : SV_Position;
    uint textureId;
};

//-------------------------------------------------------------------------------------            
// Sprite Vertex Shader
//-------------------------------------------------------------------------------------

VSSpriteOut SpriteVS(uint VID : SV_VertexID, uint SIID : SV_InstanceID)
{
    VSSpriteOut Out = (VSSpriteOut)0;

    // VID is either 0, 1, 2 or 3
    // We can map 0 to position (0,0), 1 to (0,1), 2 to (1,0), 3 to (1,1)

    // We fetch the sprite instance data accord SIID
    Sprite sdata = SpritesRO[SIID];

    // function f computes screen space vertex position
    float3 pos = f (g_mViewProjection, VID, position, rotation, scaling, layer etc)

    Out.position = pos;
    Out.textureId = sdata.textureId;

    return Out;
}

//-------------------------------------------------------------------------------------
// Sprite Pixel Shader
//-------------------------------------------------------------------------------------

float4 SpritePS(VSSpriteOut In) : SV_Target
{
    // use In.textureId to fetch the right texture slice in texture array
    return color;
}

Emblaze

Could you give me a short code example please? I struggle to get started with the buffer. – Chloris

Check out all D3D11 samples from DXSDK, and look carefully how they do for creating Buffers, binding them, updating them, etc. – Emblaze