DirectX: Draw bitmap image scale up in viewport caused low quality? - c++

Question

I'm using DirectX to draw the images with RGB data in buffer. The fllowing is sumary code:
// create the vertex buffer
D3D11_BUFFER_DESC bd;
ZeroMemory(&bd, sizeof(bd));
bd.Usage = D3D11_USAGE_DYNAMIC; // write access access by CPU and GPU
bd.ByteWidth = sizeOfOurVertices; // size is the VERTEX struct * pW*pH
bd.BindFlags = D3D11_BIND_VERTEX_BUFFER; // use as a vertex buffer
bd.CPUAccessFlags = D3D11_CPU_ACCESS_WRITE; // allow CPU to write in buffer
dev->CreateBuffer(&bd, NULL, &pVBuffer); // create the buffer
//Create Sample for texture
D3D11_SAMPLER_DESC desc;
desc.Filter = D3D11_FILTER_ANISOTROPIC;
desc.MaxAnisotropy = 16;
ID3D11SamplerState *ppSamplerState = NULL;
dev->CreateSamplerState(&desc, &ppSamplerState);
devcon->PSSetSamplers(0, 1, &ppSamplerState);
//Create list vertices from RGB data buffer
pW = bitmapSource->PixelWidth;
pH = bitmapSource->PixelHeight;
OurVertices = new VERTEX[pW*pH];
vIndex = 0;
unsigned char* curP = rgbPixelsBuff;
for (y = 0; y < pH; y++)
{
for (x = 0; x < pW; x++)
{
OurVertices[vIndex].Color.b = *curP++;
OurVertices[vIndex].Color.g = *curP++;
OurVertices[vIndex].Color.r = *curP++;
OurVertices[vIndex].Color.a = *curP++;
OurVertices[vIndex].X = x;
OurVertices[vIndex].Y = y;
OurVertices[vIndex].Z = 0.0f;
vIndex++;
}
}
sizeOfOurVertices = sizeof(VERTEX)* pW*pH;
// copy the vertices into the buffer
D3D11_MAPPED_SUBRESOURCE ms;
devcon->Map(pVBuffer, NULL, D3D11_MAP_WRITE_DISCARD, NULL, &ms); // map the buffer
memcpy(ms.pData, OurVertices, sizeOfOurVertices); // copy the data
devcon->Unmap(pVBuffer, NULL);
// unmap the buffer
// clear the back buffer to a deep blue
devcon->ClearRenderTargetView(backbuffer, D3DXCOLOR(0.0f, 0.2f, 0.4f, 1.0f));
// select which vertex buffer to display
UINT stride = sizeof(VERTEX);
UINT offset = 0;
devcon->IASetVertexBuffers(0, 1, &pVBuffer, &stride, &offset);
// select which primtive type we are using
devcon->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_POINTLIST);
// draw the vertex buffer to the back buffer
devcon->Draw(pW*pH, 0);
// switch the back buffer and the front buffer
swapchain->Present(0, 0);
When the viewport's size is smaller or equal the image's size => everything is ok. But when viewport's size is lager image's size => the image's quality is very bad.
I've searched and tried to use desc.Filter = D3D11_FILTER_ANISOTROPIC;as above code (I've tried to use D3D11_FILTER_MIN_POINT_MAG_MIP_LINEAR or D3D11_FILTER_MIN_LINEAR_MAG_MIP_POINTtoo), but the result is not better. The following images are result of displaying:
Someone can tell me the way to fix it.
Many thanks!

Answer 1

You are drawing each pixel as a point using DirectX. It is normal that when the screen size gets bigger, your points will move apart and the quality will be bad. You should draw a textured quad instead, using a texture that you fill with your RGB data and a pixel shader.