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DirectX9 3D 快速上手 6
By sssa2000
4/25/2005
讲了很多，最基础的部分就剩下纹理没有讲到了。Texture是Directx里面非常重要的一部分。为了简便起见，我们还是以SDK的Tutorial5为例子。
纹理就像一张墙纸，用来贴在物体的表面，当然，如果足够大，贴一次就能覆盖整个物体的表面，也可以用适当的方法让纹理排列成你要的效果。
来看看纹理的比较重要的函数：Device.SetTexture
public void SetTexture(
int stage, //纹理混合阶段序号，从0开始
BaseTexture texture //要设置的纹理对象
);
public void SetTextureStageState(
int stage, //纹理混合阶段序号
TextureStageStates state, // TextureStageStates enumeration的成员
int value //对应阶段状态的值
);
SetTextureStageState函数对处理不同的纹理坐标，颜色操作，Alpha操作，和凹凸映射/环境映射比较适用，但是这些操作只对DX9的固定功能的多纹理单元有效，不能将他们与像素shader连用。
public void SetSamplerState(
int stage, //纹理混合阶段序号
SamplerStageStates state, // SamplerStageStates enumeration的成员
int value //对应采样器状态的值
);
知道了这些下面读懂这些代码就很容易了，我们需要建立Vertex，这里我们需要有一点点地改变，在以前我们接触到的Vertex里面都不涉及到纹理，所以我们选择了CustomVertex里面不包括纹理的类型，现在我们要用CustomVertex.PositionNormalTextured，从名字就可以看出来，这个类型包括了法线还包括了位置的X,Y,Z，以及纹理坐标的Tu和Tv。
当然如果使用CustomVertex.PositionTextured 也是可以的，它不包括法线信息。
接下来我们需要为每个Vertex指定信息，我们先打断一下讲讲纹理坐标，为了通过指定纹理坐标来访问纹理中的每个图素，DX采用了一个一般化的编址方案，纹理地址由[0.0,1.0]区间内的坐标组成，这样我们就不用关心纹理的实际尺寸，例如可以使用(0.0f,0.0f) ,(1.0f,0.0f),(1.0f,1.0f),(0.0f,1.0f)把一个纹理贴到一个矩形上，同样如果(0.0f,0.0f) ,(0。5f,0.0f),(0.5,1.0f),(0.0f,1.0f)就是纹理的左半边。
我们可以通过TextureLoader.FromFile方法来读入图片作为纹理。
这里代码很简单里面有详细的注释，我就不多讲了，
//-----------------------------------------------------------------------------
// File: texture.cs
//
// Desc: Better than just lights and materials, 3D objects look much more
// convincing when texture-mapped. Textures can be thought of as a sort
// of wallpaper, that is shrinkwrapped to fit a texture. Textures are
// typically loaded from image files, and D3DX provides a utility to
// function to do this for us. Like a vertex buffer, textures have
// Lock() and Unlock() functions to access (read or write) the image
// data. Textures have a width, height, miplevel, and pixel format. The
// miplevel is for "mipmapped" textures, an advanced performance-
// enhancing feature which uses lower resolutions of the texture for
// objects in the distance where detail is less noticeable. The pixel
// format determines how the colors are stored in a texel. The most
// common formats are the 16-bit R5G6B5 format (5 bits of red, 6-bits of
// green and 5 bits of blue) and the 32-bit A8R8G8B8 format (8 bits each
// of alpha, red, green, and blue).
//
// Textures are associated with geometry through texture coordinates.
// Each vertex has one or more sets of texture coordinates, which are
// named tu and tv and range from 0.0 to 1.0. Texture coordinates can be
// supplied by the geometry, or can be automatically generated using
// Direct3D texture coordinate generation (which is an advanced feature).
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//-----------------------------------------------------------------------------
using System;
using System.Drawing;
using System.Windows.Forms;
using Microsoft.DirectX;
using Microsoft.DirectX.Direct3D;
using Direct3D=Microsoft.DirectX.Direct3D;
namespace TextureTutorial
{
public class Textures : Form
{
// Our global variables for this project
Device device = null; // Our rendering device
VertexBuffer vertexBuffer = null;
Texture texture = null;
PresentParameters presentParams = new PresentParameters();
bool pause = false;
public Textures()
{
// Set the initial size of our form
this.ClientSize = new System.Drawing.Size(400,300);
// And its caption
this.Text = "Direct3D Tutorial 5 - Textures";
}
public bool InitializeGraphics()
{
try
{
presentParams.Windowed=true; // We don't want to run fullscreen
presentParams.SwapEffect = SwapEffect.Discard; // Discard the frames
presentParams.EnableAutoDepthStencil = true; // Turn on a Depth stencil
presentParams.AutoDepthStencilFormat = DepthFormat.D16; // And the stencil format
device = new Device(0, DeviceType.Hardware, this, CreateFlags.SoftwareVertexProcessing, presentParams); //Create a device
device.DeviceReset += new System.EventHandler(this.OnResetDevice);
this.OnCreateDevice(device, null);
this.OnResetDevice(device, null);
pause = false;
return true;
}
catch (DirectXException)
{
// Catch any errors and return a failure
return false;
}
}
public void OnCreateDevice(object sender, EventArgs e)
{
Device dev = (Device)sender;
// Now Create the VB
vertexBuffer = new VertexBuffer(typeof(CustomVertex.PositionNormalTextured), 100, dev, Usage.WriteOnly, CustomVertex.PositionNormalTextured.Format, Pool.Default);
vertexBuffer.Created += new System.EventHandler(this.OnCreateVertexBuffer);
this.OnCreateVertexBuffer(vertexBuffer, null);
}
public void OnResetDevice(object sender, EventArgs e)
{
Device dev = (Device)sender;
// Turn off culling, so we see the front and back of the triangle
dev.RenderState.CullMode = Cull.None;
// Turn off D3D lighting
dev.RenderState.Lighting = false;
// Turn on the ZBuffer
dev.RenderState.ZBufferEnable = true;
// Now create our texture
texture = TextureLoader.FromFile(dev, Application.StartupPath + @"\..\..\banana.bmp");
}
public void OnCreateVertexBuffer(object sender, EventArgs e)
{
VertexBuffer vb = (VertexBuffer)sender;
// Create a vertex buffer (100 customervertex)
CustomVertex.PositionNormalTextured[] verts = (CustomVertex.PositionNormalTextured[])vb.Lock(0,0); // Lock the buffer (which will return our structs)
for (int i = 0; i < 50; i++)
{
// Fill up our structs
float theta = (float)(2 * Math.PI * i) / 49;
verts[2 * i].Position = new Vector3((float)Math.Sin(theta), -1, (float)Math.Cos(theta));
verts[2 * i].Normal = new Vector3((float)Math.Sin(theta), 0, (float)Math.Cos(theta));
verts[2 * i].Tu = ((float)i)/(50-1);
verts[2 * i].Tv = 1.0f;
verts[2 * i + 1].Position = new Vector3((float)Math.Sin(theta), 1, (float)Math.Cos(theta));
verts[2 * i + 1].Normal = new Vector3((float)Math.Sin(theta), 0, (float)Math.Cos(theta));
verts[2 * i + 1].Tu = ((float)i)/(50-1);
verts[2 * i + 1].Tv = 0.0f;
}
// Unlock (and copy) the data
vb.Unlock();
}
private void SetupMatrices()
{
// For our world matrix, we will just rotate the object about the y-axis.
device.Transform.World = Matrix.RotationAxis(new Vector3((float)Math.Cos(Environment.TickCount / 250.0f),1,(float)Math.Sin(Environment.TickCount / 250.0f)), Environment.TickCount / 1000.0f );
// Set up our view matrix. A view matrix can be defined given an eye point,
// a point to lookat, and a direction for which way is up. Here, we set the
// eye five units back along the z-axis and up three units, look at the
// origin, and define "up" to be in the y-direction.
device.Transform.View = Matrix.LookAtLH( new Vector3( 0.0f, 3.0f,-5.0f ), new Vector3( 0.0f, 0.0f, 0.0f ), new Vector3( 0.0f, 1.0f, 0.0f ) );
// For the projection matrix, we set up a perspective transform (which
// transforms geometry from 3D view space to 2D viewport space, with
// a perspective divide making objects smaller in the distance). To build
// a perpsective transform, we need the field of view (1/4 pi is common),
// the aspect ratio, and the near and far clipping planes (which define at
// what distances geometry should be no longer be rendered).
device.Transform.Projection = Matrix.PerspectiveFovLH( (float)Math.PI / 4.0f, 1.0f, 1.0f, 100.0f );
}
private void Render()
{
if (pause)
return;
//Clear the backbuffer to a blue color
device.Clear(ClearFlags.Target | ClearFlags.ZBuffer, System.Drawing.Color.Blue, 1.0f, 0);
//Begin the scene
device.BeginScene();
// Setup the world, view, and projection matrices
SetupMatrices();
// Setup our texture. Using textures introduces the texture stage states,
// which govern how textures get blended together (in the case of multiple
// textures) and lighting information. In this case, we are modulating
// (blending) our texture with the diffuse color of the vertices.
device.SetTexture(0,texture);
device.TextureState[0].ColorOperation = TextureOperation.Modulate;
device.TextureState[0].ColorArgument1 = TextureArgument.TextureColor;
device.TextureState[0].ColorArgument2 = TextureArgument.Diffuse;
device.TextureState[0].AlphaOperation = TextureOperation.Disable;
device.SetStreamSource(0, vertexBuffer, 0);
device.VertexFormat = CustomVertex.PositionNormalTextured.Format;
device.DrawPrimitives(PrimitiveType.TriangleStrip, 0, (4*25)-2);
//End the scene
device.EndScene();
// Update the screen
device.Present();
}
protected override void OnPaint(System.Windows.Forms.PaintEventArgs e)
{
this.Render(); // Render on painting
}
protected override void OnKeyPress(System.Windows.Forms.KeyPressEventArgs e)
{
if ((int)(byte)e.KeyChar == (int)System.Windows.Forms.Keys.Escape)
this.Dispose(); // Esc was pressed
}
protected override void OnResize(System.EventArgs e)
{
pause = ((this.WindowState == FormWindowState.Minimized) || !this.Visible);
}
/// <summary>
/// The main entry point for the application.
/// </summary>
static void Main()
{
using (Textures frm = new Textures())
{
if (!frm.InitializeGraphics()) // Initialize Direct3D
{
MessageBox.Show("Could not initialize Direct3D. This tutorial will exit.");
return;
}
frm.Show();
// While the form is still valid, render and process messages
while(frm.Created)
{
frm.Render();
Application.DoEvents();
}
}
}
}
}
这里还有一个简单的方法处理纹理，其实也差不多，看上去简单一些而已：
tex = new Texture(device, new Bitmap(this.GetType(), "puck.bmp"), Usage.Dynamic, Pool.Default);
然后在画图的时候用一句
device.SetTexture(0, tex);
就可以把纹理设置到物体上了，不过如果要进行稍微复杂的纹理操作，这个方法就不管用了。
关于纹理的东西还有很多很多，比如纹理的寻址模式，纹理包装，纹理过滤抗锯齿以及alpha混合 和多重纹理等等，这里介绍的只是九牛一毛，不过这些在后面都会慢慢介绍到。
By sssa2000
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发表于 2005-4-25 01:14:00
