Terrain rendering using Geometry Shader

Question

my idea is render an entire terrain based on heightmap using geometry shader, i am parsing only one point per quad of terrain with the heights of the corners, however for some reason i am not being able to expand every point into quads, if not wrong i should be able to do this using geometry shader directly.

Load Terrain on GPU memory -> Draw entire terrain -> Expand every point into 4 vertex -> Process texture on Pixel Shader

Vertex Input:

enum SHTerrainHeightEnum
{
    CORNER_TL, // Top-Left
    CORNER_TR, // Top-Right
    CORNER_BR, // Bottom-Right
    CORNER_BL, // Bottom-Left
    CORNER_MAX,
};

struct SHTerrainVertex // Point
{
    uint16 Index;
    float Height[CORNER_MAX];
};

Vertex Shader:

struct VertexInputType
{
    float Index : TEXCOORD0;
    float4 Heights : POSITION;
};

VertexInputType main( VertexInputType input )
{
    return input;
}

Geometry Shader:

cbuffer MatrixBuffer : register(b0)
{
    matrix worldMatrix;
    matrix viewMatrix;
    matrix projectionMatrix;
};

struct VertexInputType
{
    float Index : TEXCOORD0;
    float4 Heights : POSITION;
};

struct GeometryOutputType
{
    float4 Position : POSITION;
    float2 UV : TEXCOORD0;
};

[maxvertexcount(4)]
void main(
    point VertexInputType input[1], 
    inout TriangleStream< GeometryOutputType > output
)
{
    float x = (float)((uint)input[0].Index % 256) * 100.0f, y = (float)((uint)input[0].Index / 256) * 100.0f;

    GeometryOutputType vertex;

    // Top Left
    vertex.Position = float4(x, y, input[0].Heights[0], 1.0f);
    vertex.UV = float2(0.0f, 0.0f);
    vertex.Position = mul(vertex.Position, worldMatrix);
    vertex.Position = mul(vertex.Position, viewMatrix);
    vertex.Position = mul(vertex.Position, projectionMatrix);
    output.Append(vertex);

    // Top Right
    vertex.Position = float4(x + 100.0f, y, input[0].Heights[1], 1.0f);
    vertex.UV = float2(1.0f, 0.0f);
    vertex.Position = mul(vertex.Position, worldMatrix);
    vertex.Position = mul(vertex.Position, viewMatrix);
    vertex.Position = mul(vertex.Position, projectionMatrix);
    output.Append(vertex);

    // Bottom Right
    vertex.Position = float4(x + 100.0f, y + 100.0f, input[0].Heights[2], 1.0f);
    vertex.UV = float2(1.0f, 1.0f);
    vertex.Position = mul(vertex.Position, worldMatrix);
    vertex.Position = mul(vertex.Position, viewMatrix);
    vertex.Position = mul(vertex.Position, projectionMatrix);
    output.Append(vertex);

    // Bottom Left
    vertex.Position = float4(x, y + 100.0f, input[0].Heights[3], 1.0f);
    vertex.UV = float2(0.0f, 1.0f);
    vertex.Position = mul(vertex.Position, worldMatrix);
    vertex.Position = mul(vertex.Position, viewMatrix);
    vertex.Position = mul(vertex.Position, projectionMatrix);
    output.Append(vertex);
}

Pixel Shader: struct GeometryOutputType { float4 Position : POSITION; float2 UV : TEXCOORD0; };

float4 main(GeometryOutputType input) : SV_TARGET
{
    return float4(0.0f, 0.5f, 0.0f, 1.0f);
}

Render Code:

uint32 TERRAIN_SIZE = 256;
VideoManager::_DeviceContext->VSSetShader(Shader::VertexShader[Shader::VS_TERRAIN], nullptr, 0);
VideoManager::_DeviceContext->GSSetShader(Shader::GeometryShader[Shader::GS_TERRAIN], nullptr, 0);
VideoManager::_DeviceContext->PSSetShader(Shader::PixelShader[Shader::PS_TERRAIN], nullptr, 0);

uint32 stride = sizeof(SHTerrainVertex), offset = 0;
VideoManager::_DeviceContext->IASetVertexBuffers(0, 1, &_VertexBuffer, &stride, &offset);
VideoManager::_DeviceContext->IASetInputLayout(Shader::InputLayout[Shader::VS_TERRAIN]);
VideoManager::_DeviceContext->IASetPrimitiveTopology(D3D11_PRIMITIVE_TOPOLOGY_POINTLIST);

VideoManager::_DeviceContext->GSSetConstantBuffers(0, 1, &_SettingBuffer);

VideoManager::_DeviceContext->Draw(TERRAIN_SIZE * TERRAIN_SIZE, 0);

VideoManager::_DeviceContext->GSSetShader(nullptr, nullptr, 0);

I couldn't figure out what is wrong with this code, it should draw on screen perfectly however it doesn't draw anything, everything is blank.

I did this for decrease the memory usage and do GPU culling of the terrain discarding the terrain blocks what are outside of camera.

EDIT: I am using DirectX 11 with feature levels of 10.0, if someone has a better recommendation about what I could do for optimize the terrain I will really appreciate

Max terrain size is 256x256, but might be extended to 1024x1024.

Any answer is appreciated, really thanks for your time.

Answer 1

Forgot to answer for mark it as answered.

At the end I finished doing what Balint recommended me, really thanks Balint for your answer.