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sepoto

Viewing Frustum.

2 posts in this topic

//--------------------------------------------------------------------------------------
// File: Tutorial01.cpp
//
// This application demonstrates creating a Direct3D 11 device
//
// http://msdn.microsoft.com/en-us/library/windows/apps/ff729718.aspx
//
// THIS CODE AND INFORMATION IS PROVIDED "AS IS" WITHOUT WARRANTY OF
// ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO
// THE IMPLIED WARRANTIES OF MERCHANTABILITY AND/OR FITNESS FOR A
// PARTICULAR PURPOSE.
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//--------------------------------------------------------------------------------------
#include <windows.h>
#include <d3d11_1.h>
#include <directxcolors.h>
#include "resource.h"

using namespace DirectX;

//--------------------------------------------------------------------------------------
// Global Variables
//--------------------------------------------------------------------------------------
HINSTANCE               g_hInst = nullptr;
HWND                    g_hWnd = nullptr;
D3D_DRIVER_TYPE         g_driverType = D3D_DRIVER_TYPE_NULL;
D3D_FEATURE_LEVEL       g_featureLevel = D3D_FEATURE_LEVEL_11_0;
ID3D11Device*           g_pd3dDevice = nullptr;
ID3D11Device1*          g_pd3dDevice1 = nullptr;
ID3D11DeviceContext*    g_pImmediateContext = nullptr;
ID3D11DeviceContext1*   g_pImmediateContext1 = nullptr;
IDXGISwapChain*         g_pSwapChain = nullptr;
ID3D11RenderTargetView* g_pRenderTargetView = nullptr;


//--------------------------------------------------------------------------------------
// Forward declarations
//--------------------------------------------------------------------------------------
HRESULT InitWindow( HINSTANCE hInstance, int nCmdShow );
HRESULT InitDevice();
void CleanupDevice();
LRESULT CALLBACK    WndProc( HWND, UINT, WPARAM, LPARAM );
void Render();


//--------------------------------------------------------------------------------------
// Entry point to the program. Initializes everything and goes into a message processing 
// loop. Idle time is used to render the scene.
//--------------------------------------------------------------------------------------
int WINAPI wWinMain( _In_ HINSTANCE hInstance, _In_opt_ HINSTANCE hPrevInstance, _In_ LPWSTR lpCmdLine, _In_ int nCmdShow )
{
    UNREFERENCED_PARAMETER( hPrevInstance );
    UNREFERENCED_PARAMETER( lpCmdLine );

    if( FAILED( InitWindow( hInstance, nCmdShow ) ) )
        return 0;

    if( FAILED( InitDevice() ) )
    {
        CleanupDevice();
        return 0;
    }

    // Main message loop
    MSG msg = {0};
    while( WM_QUIT != msg.message )
    {
        if( PeekMessage( &msg, nullptr, 0, 0, PM_REMOVE ) )
        {
            TranslateMessage( &msg );
            DispatchMessage( &msg );
        }
        else
        {
            Render();
        }
    }

    CleanupDevice();

    return ( int )msg.wParam;
}


//--------------------------------------------------------------------------------------
// Register class and create window
//--------------------------------------------------------------------------------------
HRESULT InitWindow( HINSTANCE hInstance, int nCmdShow )
{
    // Register class
    WNDCLASSEX wcex;
    wcex.cbSize = sizeof( WNDCLASSEX );
    wcex.style = CS_HREDRAW | CS_VREDRAW;
    wcex.lpfnWndProc = WndProc;
    wcex.cbClsExtra = 0;
    wcex.cbWndExtra = 0;
    wcex.hInstance = hInstance;
    wcex.hIcon = LoadIcon( hInstance, ( LPCTSTR )IDI_TUTORIAL1 );
    wcex.hCursor = LoadCursor( nullptr, IDC_ARROW );
    wcex.hbrBackground = ( HBRUSH )( COLOR_WINDOW + 1 );
    wcex.lpszMenuName = nullptr;
    wcex.lpszClassName = L"TutorialWindowClass";
    wcex.hIconSm = LoadIcon( wcex.hInstance, ( LPCTSTR )IDI_TUTORIAL1 );
    if( !RegisterClassEx( &wcex ) )
        return E_FAIL;

    // Create window
    g_hInst = hInstance;
    RECT rc = { 0, 0, 640, 480 };
    AdjustWindowRect( &rc, WS_OVERLAPPEDWINDOW, FALSE );
    g_hWnd = CreateWindow( L"TutorialWindowClass", L"Direct3D 11 Tutorial 1: Direct3D 11 Basics", WS_OVERLAPPEDWINDOW,
                           CW_USEDEFAULT, CW_USEDEFAULT, rc.right - rc.left, rc.bottom - rc.top, nullptr, nullptr, hInstance,
                           nullptr );
    if( !g_hWnd )
        return E_FAIL;

    ShowWindow( g_hWnd, nCmdShow );

    return S_OK;
}


//--------------------------------------------------------------------------------------
// Called every time the application receives a message
//--------------------------------------------------------------------------------------
LRESULT CALLBACK WndProc( HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam )
{
    PAINTSTRUCT ps;
    HDC hdc;

    switch( message )
    {
        case WM_PAINT:
            hdc = BeginPaint( hWnd, &ps );
            EndPaint( hWnd, &ps );
            break;

        case WM_DESTROY:
            PostQuitMessage( 0 );
            break;

        default:
            return DefWindowProc( hWnd, message, wParam, lParam );
    }

    return 0;
}


//--------------------------------------------------------------------------------------
// Create Direct3D device and swap chain
//--------------------------------------------------------------------------------------
HRESULT InitDevice()
{
    HRESULT hr = S_OK;

    RECT rc;
    GetClientRect( g_hWnd, &rc );
    UINT width = rc.right - rc.left;
    UINT height = rc.bottom - rc.top;

    UINT createDeviceFlags = 0;
#ifdef _DEBUG
    createDeviceFlags |= D3D11_CREATE_DEVICE_DEBUG;
#endif

    D3D_DRIVER_TYPE driverTypes[] =
    {
        D3D_DRIVER_TYPE_HARDWARE,
        D3D_DRIVER_TYPE_WARP,
        D3D_DRIVER_TYPE_REFERENCE,
    };
    UINT numDriverTypes = ARRAYSIZE( driverTypes );

    D3D_FEATURE_LEVEL featureLevels[] =
    {
        D3D_FEATURE_LEVEL_11_1,
        D3D_FEATURE_LEVEL_11_0,
        D3D_FEATURE_LEVEL_10_1,
        D3D_FEATURE_LEVEL_10_0,
    };
	UINT numFeatureLevels = ARRAYSIZE( featureLevels );

    DXGI_SWAP_CHAIN_DESC sd;
    ZeroMemory( &sd, sizeof( sd ) );
    sd.BufferCount = 1;
    sd.BufferDesc.Width = width;
    sd.BufferDesc.Height = height;
    sd.BufferDesc.Format = DXGI_FORMAT_R8G8B8A8_UNORM;
    sd.BufferDesc.RefreshRate.Numerator = 60;
    sd.BufferDesc.RefreshRate.Denominator = 1;
    sd.BufferUsage = DXGI_USAGE_RENDER_TARGET_OUTPUT;
    sd.OutputWindow = g_hWnd;
    sd.SampleDesc.Count = 1;
    sd.SampleDesc.Quality = 0;
    sd.Windowed = TRUE;

    for( UINT driverTypeIndex = 0; driverTypeIndex < numDriverTypes; driverTypeIndex++ )
    {
        g_driverType = driverTypes[driverTypeIndex];
        hr = D3D11CreateDeviceAndSwapChain( nullptr, g_driverType, nullptr, createDeviceFlags, featureLevels, numFeatureLevels,
                                            D3D11_SDK_VERSION, &sd, &g_pSwapChain, &g_pd3dDevice, &g_featureLevel, &g_pImmediateContext );

        if ( hr == E_INVALIDARG )
        {
            // DirectX 11.0 platforms will not recognize D3D_FEATURE_LEVEL_11_1 so we need to retry without it
            hr = D3D11CreateDeviceAndSwapChain( nullptr, g_driverType, nullptr, createDeviceFlags, &featureLevels[1], numFeatureLevels - 1,
                                                D3D11_SDK_VERSION, &sd, &g_pSwapChain, &g_pd3dDevice, &g_featureLevel, &g_pImmediateContext );
        }

        if( SUCCEEDED( hr ) )
            break;
    }
    if( FAILED( hr ) )
        return hr;

    // Obtain the Direct3D 11.1 versions if available
    hr = g_pd3dDevice->QueryInterface( __uuidof( ID3D11Device1 ), reinterpret_cast<void**>( &g_pd3dDevice1 ) );
    if ( SUCCEEDED(hr) )
    {
        (void)g_pImmediateContext->QueryInterface( __uuidof( ID3D11DeviceContext1 ), reinterpret_cast<void**>( &g_pImmediateContext1 ) );
    }

    // Create a render target view
    ID3D11Texture2D* pBackBuffer = nullptr;
    hr = g_pSwapChain->GetBuffer( 0, __uuidof( ID3D11Texture2D ), reinterpret_cast<void**>( &pBackBuffer ) );
    if( FAILED( hr ) )
        return hr;

    hr = g_pd3dDevice->CreateRenderTargetView( pBackBuffer, nullptr, &g_pRenderTargetView );
    pBackBuffer->Release();
    if( FAILED( hr ) )
        return hr;

    g_pImmediateContext->OMSetRenderTargets( 1, &g_pRenderTargetView, nullptr );

    // Setup the viewport
    D3D11_VIEWPORT vp;
    vp.Width = (FLOAT)width;
    vp.Height = (FLOAT)height;
    vp.MinDepth = 0.0f;
    vp.MaxDepth = 1.0f;
    vp.TopLeftX = 0;
    vp.TopLeftY = 0;
    g_pImmediateContext->RSSetViewports( 1, &vp );

    return S_OK;
}


//--------------------------------------------------------------------------------------
// Render the frame
//--------------------------------------------------------------------------------------
void Render()
{
    // Just clear the backbuffer
    g_pImmediateContext->ClearRenderTargetView( g_pRenderTargetView, Colors::MidnightBlue );
    g_pSwapChain->Present( 0, 0 );
}


//--------------------------------------------------------------------------------------
// Clean up the objects we've created
//--------------------------------------------------------------------------------------
void CleanupDevice()
{
    if( g_pImmediateContext ) g_pImmediateContext->ClearState();

    if( g_pRenderTargetView ) g_pRenderTargetView->Release();
    if( g_pSwapChain ) g_pSwapChain->Release();
    if( g_pImmediateContext1 ) g_pImmediateContext1->Release();
    if( g_pImmediateContext ) g_pImmediateContext->Release();
    if( g_pd3dDevice1 ) g_pd3dDevice1->Release();
    if( g_pd3dDevice ) g_pd3dDevice->Release();
}

I've referenced the code against my book "Introduction to 3D Grame Programming" by Frank D. Luna. I think I have a good understanding of what it does and now my question is about setting up a viewing frustum. I would like to set up a viewpoint from somewhere like (0,0,100) looking down the Z axis to the point (0,0,0) so I can draw some lines, curves and polygonal areas on the XY plane at Z=0. I will need to know the coordinates of the rectangular area that is visible by the viewpoint on the XY plane at Z=0.

 

From my studies on frustums there is a front clipping plane and a back clipping plane. I am looking at a diagram:

http://msdn.microsoft.com/en-us/library/ff634570.aspx

 

so right now it is not clear to me which clipping plane is Z=0 or how to find the coordinates of the clipping plane rectangle.

 

Thanks for any help on this...

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For the type of rendering you're describing (lines and curves that all drawn on a flat plane), it sounds like you want to use an orthographic projection. With an orthographic projection the size of something on the screen doesn't depend on its distance from the camera, it only depends on the width and the height of the projection that you create. So for instance you could set up a projection that's 100 units wide and 100 units tall, and then something located at (50, 50) on the XY plane will end up being drawn in the top right corner. The resulting projection volume ends up being a basically a 3D box, rather than the frustum shape that you get from a perspective projection. Are you using a math library yet, such as DirectXMath? Any decent math library will have functions for setting up an orthographic projection matrix given a few parameters.

 

Typically you only want a perspective projection if you're doing 3D rendering, where things will be drawn at varying depths and you need perspective applied so that closer objects end up being larger than further objects.

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So for instance you could set up a projection that's 100 units wide and 100 units tall, and then something located at (50, 50) on the XY plane will end up being drawn in the top right corner.

For clarity, the simplest (and possibly most common) forms of orthographic projections put [0,0] in the upper left or lower left, so [50,50] would then be in the middle of the screen.
For [50,50] to be in one of the corners you would use an “offset” or “off-center” orthographic projection.

In Direct3D 9 these were created via D3DXMatrixOrthoLH() and D3DXMatrixOrthoOffCenterLH() respectively.  The math for each is shown in the links if you aren’t using a math library and want to brew your own.

 

 

L. Spiro

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