Beginning direct3d gameprogramming04_3dfundamentals_20160414_jintaeks

Beginning Direct3D Game Programming:
4. 3D Fundamentals
jintaeks@gmail.com
Division of Digital Contents, DongSeo University.
April 2016

Presentation outline
 Work with vertices and orientation
 Work with faces and polygons
 Use Gouraud shading
 Put into practice the basics of texture mapping
2

3D Fundamentals
 The Direct3D engine uses a left-handed coordinate system
by default.
 The OpenGL coordinate system uses a positive z-axis that
points out of the screen. This is called a right-handed
coordinate system.
3

vertex
 The square uses four vertices, v1 through v4.
 A vertex defines the point of intersection of one or more
lines;
 Direct3D needs a way to place these primitives in a scene.
4

 To define a vertex in 3D space, you must specify three
coordinate values: x, y, and z.
v1 (0, 0, 0)
v2 (0, 2, 0)
v3 (0, 2, 2)
v4 (0, 0, 2)
 You can define the location of a vertex by specifying a
vector from the origin to another point in 3D space.
5

vector
 They are mathematical entities that describe a direction and a
magnitude (which can be used for velocity, for example).
 Vectors are usually denoted by a bold-faced letter, such as a.
 Thus you could say the vector v = (1, 0, 1).
 Vectors are not only used to define the position of the
vertices, they are also used to define a direction.
6

D3DXVECTOR
typedef struct D3DXVECTOR3 {
FLOAT x;
FLOAT y;
FLOAT z;
} D3DXVECTOR3, *LPD3DXVECTOR3;
#ifdef __cplusplus
typedef struct D3DXVECTOR3 : public D3DVECTOR
{
public:
D3DXVECTOR3() {};
D3DXVECTOR3( CONST D3DVECTOR& );
D3DXVECTOR3( FLOAT x, FLOAT y, FLOAT z );
// assignment operators
D3DXVECTOR3& operator += ( CONST D3DXVECTOR3& );
D3DXVECTOR3& operator -= ( CONST D3DXVECTOR3& );
D3DXVECTOR3& operator *= ( FLOAT );
7

Understanding Vertices
 Vector is often used to describe the position of a vertex.
Nevertheless, a vertex consists of much more data than the
position.
struct Vertex
{
D3DVECTOR3 vPosition;
DWORD dwDiffuse; // diffuse vertex color
D3DVECTOR3 vNormal; // vertex normal
FLOAT u, v; // texture coordinates of vertex
}
 All vertices are stored in a vertex buffer.
8

Working with Orientation
 You might describe the orientation of an object by using at
least four vectors—LOOK, UP, RIGHT, and POSITION.
9

Understanding Faces
 Any 3D object consists of faces, as shown in Figure 4.6.
10

 Every model and 3D world is broken down into points, lines,
and triangles, the only primitives Direct3D is able to render.
 If you design your shapes using polygons with four or more
vertices to reduce the number of faces, Direct3D will divide
every face into triangles.
11

Backface Culling
 Direct3D can cull back faces.
 Backface Culling uses the cross-product of two sides of a
triangle to calculate a vector that is perpendicular to the plane
that is formed by the two sides.
12

D3DCULL
typedef enum D3DCULL {
D3DCULL_NONE = 1,
D3DCULL_CW = 2,
D3DCULL_CCW = 3,
D3DCULL_FORCE_DWORD = 0x7fffffff
} D3DCULL, *LPD3DCULL;
13

Understanding Polygons
 A polygon can be defined in either 2D or 3D space.
 We will refer to polygons as n-sided closed figures defined by
at least three vertices.
 The simplest polygon is a triangle.
 Direct3D uses triangles to compose most polygons because
all three vertices in a triangle are guaranteed to be co-planar.
14

Understanding Normals
 Normals are perpendicular vectors that can be used to define
the direction a face is pointing or the visible side of a face.
 A vertex normal is often perpendicular to a face, and it
usually sits upon the vertex as one unit long.
 The other type of normal is a face normal. It is usually
perpendicular to a face and sits in the middle of the face.
15

Understanding Normals and Gouraud
Shading
 Shading is the process of performing lighting computations
and determining pixel colors from them.
16

Gouraud Shading
 The vertex normal vector is used in Gouraud shading mode
(the default shading mode since the advent of Direct3D 6.0)
to control lighting and to make some texturing effects.
17

Comparison of Shading Models
18

Texture-Mapping Basics
 Texture refers to a special kind of image that you can map
onto a face or multiple faces.
19

Texture Coordinates in Direct3D
 It uses a generic addressing scheme in which all texel
addresses are in the range of 0.0 to 1.0, inclusive.
20

• Illustration of pixel (a square of color) that is mapped into
object space
21

 You can assign parts of a texture to a primitive by using
texture coordinates.
 If you want to texture a triangle, it could work something like
Figure 4.13.
cvVertices [0] = {0.0f, 0.0f, 0.5f, 1.0f, 0.0f, 0.0f}; // x, y, z, rhw, tu, tv
cvVertices [1] = {1.0f, 0.0f, 0.5f, 1.0f, 1.0f, 0.0f};
22

Beginning direct3d gameprogramming04_3dfundamentals_20160414_jintaeks

Beginning direct3d gameprogramming04_3dfundamentals_20160414_jintaeks

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