Hands On DarkBASIC Pro - Digital Skills

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FIG-30.9 A 3D Vector Object Terminology FIG-30.10 A Cube - An Example of a Primitive FIG-30.11 We can visualise a 3D vector object as shown in FIG-30.9. A 3D Vector 12.3 4.6 1.7 x y z The 3D vector holds three values... ...an x value, a y value and a z value Many of the DarkBASIC Pro statements we'll encounter later make use of 3D vectors for storing results, so it's useful to give you this quick grounding in them at this early stage. We'll learn more on this subject in a later chapter. Just as 2D has a few basic shapes such as a line, a circle, a triangle and a rectangle, so we have a set of basic shapes (known as primitives) in 3D. These include the sphere, cylinder, cone, and cube. In FIG-30.10 we see and example of a cube. solid wireframe The cube is shown in two ways: solid, with shading caused by the light falling on its surface, and wireframe showing how the cube is constructed. Polygon is the term used for a many-sided enclosed area. The simplest polygon (that is, the one with the least sides) is the triangle. The point where two lines of a polygon meet is known as a vertex. A triangle has three vertices (see FIG-20.11). The Vertices of a Triangle Vetrices FIG-30.12 Edges Triangle The line between two vertices is known as an edge (see FIG-30.12). Edges Every 3D shape in a game is constructed from polygons (normally triangles), as you can see from the wireframe version of the cube shown in FIG-30.10. The greater the number of polygons used to create an object, the more detailed and realistic it will appear (see FIG-30.13). But there is a price to pay for greater detail DarkBASIC Pro: 3D - Concepts and Terminology 749
FIG-30.13 Varying the Polygons in a Sphere FIG-30.14 Textures Adding Texture to a 3D Object - higher processing requirements. As you increase the number of polygons that go to make up the objects in your scene, the harder your processor and video card need to work. Ask too much of your hardware, and screen updating will slow down. The number of times the screen is redrawn in one second is known as the frame rate and is quoted in frames per second (fps). If the frame rate falls much below about 20 fps, then your eyes will become aware of the screen refreshing and the picture will become jerky. In solid mode (as opposed to wireframe), a 3D object has a bland grey surface, but we can use an image wrapped around that object to give it a greater reality. By wrapping the image of riveted steel plate round a sphere, we can create the illusion of a metal ball. Wrap an image of wooden planks round the same sphere and we create a wooden ball (see FIG-30.14). Images with an Alpha Channel A Sphere with Few Polygons A Sphere with Many Polygons The image used to texture an object can be one of many different formats. For example, JPG and BMP files are often used, but sometimes we will see images stored in the PNG or TGA format. PNG and TGA files are amongst those formats capable of embedding an alpha channel within the image. An alpha channel affects how visible an image is and is probably best explained with an analogy. Imagine you've just painted an image on a piece of glass and that the light illuminating the picture comes from behind the glass (see FIG-30.15) - like looking 750 DarkBASIC Pro: 3D - Concepts and Terminology
Page 1 and 2: Hands On DarkBASIC Pro A Self-Study
Page 3 and 4: Copyright © Alistair Stewart 2006
Page 5 and 6: The TURN OBJECT Statement . . . . .
Page 7 and 8: The YROTATE CAMERA Statement . . .
Page 9 and 10: Chapter 35 Meshes and Limbs Meshes.
Page 11 and 12: The OBJECT IN SCREEN Statement . .
Page 13 and 14: The MAKE OBJECT COLLISION BOX State
Page 15 and 16: Adding MoveElevator() . . . . . . .
Page 17 and 18: The RANDOMIZE MATRIX Statement . .
Page 19 and 20: The MAKE MEMBLOCK FROM SOUND Statem
Page 21 and 22: The TRANSPOSE MATRIX4 Statement . .
Page 23 and 24: Networking the Game . . . . . . . .
Page 25 and 26: Acknowledgements I would like to th
Page 27 and 28: Syntax Diagrams make only a half-he
Page 29 and 30: The 3D World Introduction The Coord
Page 31 and 32: FIG-30.4 Points Determining the Pos
Page 33: FIG-30.6 Rotation A Cuboid is Rotat
Page 37 and 38: FIG-30.17 Lights Surface Normals FI
Page 39 and 40: � Space within the 3D world is me
Page 41 and 42: 3D Primitives Introduction FIG-31.1
Page 43 and 44: FIG-31.5 The MAKE OBJECT BOX Statem
Page 45 and 46: FIG-31.9 The MAKE OBJECT CONE State
Page 47 and 48: FIG-31.13 Creating a Triangle Objec
Page 49 and 50: FIG-31.16 The MOVE OBJECT Statement
Page 51 and 52: FIG-31.19 Possible Rotations about
Page 53 and 54: LISTING-31.3 Rotating an Object abo
Page 55 and 56: FIG-31.29 The PITCH OBJECT Statemen
Page 57 and 58: FIG-31.32 The POINT OBJECT Statemen
Page 59 and 60: LISTING-31.6 (continued) Local Axes
Page 61 and 62: LISTING-31.7 Resizing an Object REM
Page 63 and 64: Copying a 3D Object FIG-31.43 The C
Page 65 and 66: FIG-31.46 FIG-31.47 The OBJECT POSI
Page 67 and 68: FIG-31.49 The OBJECT ANGLE Statemen
Page 69 and 70: LISTING-31.11 (continued) Switching
Page 71 and 72: FIG-31.53 The SET GLOBAL OBJECT CRE
Page 73 and 74: Merging Primitives Introduction FIG
Page 75 and 76: FIG-31.58 As you've just discovered
Page 77 and 78: Solutions Activity 31.1 No solution
Page 79 and 80: Activity 31.20 The duplicated cube
Page 81 and 82: 796 DarkBASIC Pro: 3D Primitives
Page 83 and 84: Adding Texture Introduction FIG-32.
Page 85 and 86:
FIG-32.3 An Image with Added Mipmap
Page 87 and 88:
FIG-32.5 Floor Texturing FIG-32.6 T
Page 89 and 90:
Seamless Tiling FIG-32.10 A Visible
Page 91 and 92:
FIG-32.12 The PLAY ANIMATION TO IMA
Page 93 and 94:
LISTING-32.6 (continued) Using the
Page 95 and 96:
The SET OBJECT TRANSPARENCY Stateme
Page 97 and 98:
LISTING-32.9 Using a Secondary Text
Page 99 and 100:
LISTING-32.10 (continued) Using the
Page 101 and 102:
FIG-32.24 A Transparent Cube Activi
Page 103 and 104:
FIG-32.27 The FADE OBJECT Statement
Page 105 and 106:
Images with an Alpha Channel Introd
Page 107 and 108:
Creating a Complex 3D Shape Introdu
Page 109 and 110:
The Code LISTING-32.15 Drawing the
Page 111 and 112:
LISTING-32.15 (continued) Drawing t
Page 113 and 114:
Sky Spheres FIG-32.32 Using a Sky S
Page 115 and 116:
Summary To cure the problem of an i
Page 117 and 118:
REM *** Create and texture plain ob
Page 119:
TEXTURE OBJECT GroundObj,CobbleImg
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