D3DHardwareOcclusionQuery.cs :  » Game » RealmForge » Axiom » RenderSystems » DirectX9 » C# / CSharp Open Source

#region LGPL License
/*
Axiom Game Engine Library
Copyright (C) 2003  Axiom Project Team

The overall design, and a majority of the core engine and rendering code 
contained within this library is a derivative of the open source Object Oriented 
Graphics Engine OGRE, which can be found at http://ogre.sourceforge.net.  
Many thanks to the OGRE team for maintaining such a high quality project.

This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later version.

This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#endregion

using System;
using Axiom.Core;
using Axiom.Graphics;
using Microsoft.DirectX;
using Microsoft.DirectX.Direct3D;
using D3DMicrosoft.DirectX.Direct3D;

namespace Axiom.RenderSystems.DirectX9{
  /// <summary>
  ///    Direct3D implementation of a hardware occlusion query.
  /// </summary>
  // Original Author: Lee Sandberg
  public class D3DHardwareOcclusionQuery : IHardwareOcclusionQuery {
    #region Fields

    /// <summary>
    ///    Reference to the current Direct3D device object.
    /// </summary>
    private D3D.Device device;
    /// <summary>
    ///    Reference to the query object being used.
    /// </summary>
    private D3D.Query query;
    /// <summary>
    ///    Number of fragments returned from the last query.
    /// </summary>
    private int lastFragmentCount;
    /// <summary>
    ///    Flag that indicates whether hardware queries are supported
    /// </summary>
    private bool isSupported;
    /// <summary>
    ///    Rate at which queries are skipped (in frames).
    /// </summary>
    private int skipRate;
    /// <summary>
    ///    Current count of number of skipped frames since query last ran.
    /// </summary>
    private int skipCounter;

    #endregion Fields

    #region Constructor

    /// <summary>
    ///    Default constructor.
    /// </summary>
    /// <param name="device">Reference to a Direct3D device.</param>
    public D3DHardwareOcclusionQuery(D3D.Device device) {
      this.device = device;

      // check if queries are supported
      isSupported = Root.Instance.RenderSystem.Caps.CheckCap(Capabilities.HardwareOcculusion);

      if(isSupported) {
        // attempt to create an occlusion query
        query = new D3D.Query(device, QueryType.Occlusion);
      }
    }

    #endregion Constructor

    #region IHardwareOcclusionQuery Members

    public void Begin() {
      // proceed if supported, or silently fail otherwise
      if(isSupported) {
        if(skipCounter == skipRate) {
          skipCounter = 0;
        }

        if(skipCounter == 0) { // && lastFragmentCount != 0) {
          query.Issue(IssueFlags.Begin);
        }
      }
    }

    public int PullResults(bool flush) {
      // default to returning a high count.  will be set otherwise if the query runs
      lastFragmentCount = 100000;

      if(isSupported) {
        lastFragmentCount = (int)query.GetData(typeof(int), flush);
      }

      return lastFragmentCount;
    }

    public void End() {
      // proceed if supported, or silently fail otherwise
      if(isSupported) {
        if(skipCounter == 0) { // && lastFragmentCount != 0) {
          query.Issue(IssueFlags.End);
        }

        skipCounter++;
      }
    }

    /// <summary>
    ///    Rate (in frames) at which queries are skipped.
    /// </summary>
    public int SkipRate {
      get {
        return skipRate;
      }
      set {
        skipRate = value;
      }
    }

    /// <summary>
    ///    Gets the number of fragments returned from the last execution of this query.
    /// </summary>
    public int LastFragmentCount {
      get {
        return lastFragmentCount;
      }
    }

    #endregion
  }
}