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).

//-----------------------------------------------------------------------------

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