Tutorial 4 - Texturing a quad
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Hi there again everyone. How did you enjoy those spinning triangles?
Today we are going to be looking at how to texture a quad (2 triangles form
a quad). We are going to build the quad in the order given in the image below.
Texturing quads is a really easy method. It involves placing what they call
UV coordinates (Texture coordinates). UV coordinates (Texure coordinates) are
used to tell direct3d how to map the texture points to the object. Look at the
image below. It shows the UV coordinates for a face on a cube.
Let's move on. We are going
to be using the CustomVertex.PositionTextured vertex format and create and texture
our quad. The most important part of this exercise is the use of the Texture
class. For a better understanding. Let's take an extract out of the SDK Docs.
"Early computer-generated 3-D images, although generally advanced for their
time, tended to have a shiny plastic look. They lacked the types of markings—such
as scuffs, cracks, fingerprints, and smudges—that give 3-D objects realistic
visual complexity. In recent years, textures have gained popularity among developers
as a tool for enhancing the realism of computer-generated 3-D images.
In its
everyday use, the word texture refers to an object's smoothness or roughness.
In computer graphics, however, a texture is a bitmap of pixel colors that give
an object the appearance of texture.
Because
Microsoft Direct3D textures are bitmaps, any bitmap can be applied to a Direct3D
primitive. For instance, applications can create and manipulate objects that
appear to have a wood grain pattern in them. Grass, dirt, and rocks can be applied
to a set of 3-D primitives that form a hill. The result is a realistic-looking
hillside. Textures also can be used to create effects such as signs along a
road, rock strata in a cliff, or the appearance of marble on a floor.
In addition,
Direct3D supports more advanced texturing techniques such as texture blending—with
or without transparency—and light mapping.
If an
application creates a hardware abstraction layer (HAL) device or a software
device, it can use 8, 16, 24, 32, 64, or 128-bit textures."
Armed with some more knowledge on Textures. We are
going to create a texture from file. Direct3D is one step ahead of us. It provides
us with a TextureLoader class. The class has a method that creates a texture
from file and is called FromFile(). The First parameter it takes is the Device
and the second is a string that contains the path to the file. Let's look at
the code.
public
void
createQuad()
{
texture = TextureLoader.FromFile(direct3d.XilathDevice,
"crate.jpg"); //Load the image from the file
CustomVertex.PositionTextured[]
quad = new CustomVertex.PositionTextured[4];
quad[0] = new
CustomVertex.PositionTextured(-1.0f, 0.0f, 0.0f, 0.0f, 1.0f);
quad[1] = new
CustomVertex.PositionTextured(-1.0f, 2.0f, 0.0f, 0.0f, 0.0f);
quad[2] = new
CustomVertex.PositionTextured( 1.0f, 0.0f, 0.0f, 1.0f, 1.0f);
quad[3] = new
CustomVertex.PositionTextured( 1.0f, 2.0f, 0.0f, 1.0f, 0.0f);
vb
= new VertexBuffer(typeof(CustomVertex.PositionTextured),
4, direct3d.XilathDevice, Usage.WriteOnly, CustomVertex.PositionTextured.Format,
Pool.Managed);
GraphicsStream stm = vb.Lock(0, 0, 0);
stm.Write(quad);
vb.Unlock();
worldMatrix.Translate(0.0f, -1.0f, 0.0f);
}
private Texture texture;
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Now that we have loaded the texture and stored the quad into the Vertex Buffer.
Let's render the quad.
Note: When we set the texture we are telling direct3d that any object rendered
after that call should be rendered with that texture. So keep this in mind. If
you want to set the texture to nothing just do SetTexture(0, 0);
public void Render()
{
direct3d.BeginRender(Color.Black); //render
our scene with the background as black
direct3d.XilathDevice.Transform.World =
worldMatrix;
direct3d.XilathDevice.SetTexture(0, texture);
//Here we tell direct3d that anything after this
method should be rendered with this texture
direct3d.XilathDevice.SetStreamSource(0,
vb, 0);
direct3d.XilathDevice.VertexFormat = CustomVertex.PositionTextured.Format;
direct3d.XilathDevice.DrawPrimitives(PrimitiveType.TriangleStrip,
0, 2);
direct3d.FinishRender();
//finish rendering our scene
}
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