4. Data structure

In this chapter, we will explain the model data handled by Sega Saturn, the specifications of material names, and the structure of texture data.

4-1. Model data specifications

The model data here refers to a set of three data: point data of three-dimensional coordinates (x, y, x), polygon data formed by four of them, and attribute data representing the attributes of the polygon. increase.
The general format when the model name is assumed to be "label" is shown below.

Point data

---

POINT point_label [] = {   
      POStoFIXED (x, y, z),
      POStoFIXED (x, y, z),
      POStoFIXED (x, y, z),
      POStoFIXED (x, y, z),
           .............
      };                
	

POINT: Point data　
x, y, z: Float type coordinate values

It is an index of 0, 1, 2, and 3 point data in order from the top.

Polygon data

---

POLYGON polygon_label [] = {
     NORMAL (x, y, z),      
     VERTICES (0,1,2,3),  
                         
     NORMAL (x, y, z),      
     VERTICES (0,1,2,3),  
          .............  
    };                   
	

NORMAL: normal vector　
x, y, z: Float type coordinate values　
VERTICES: Point data of 4 points forming a polygon

In the case of a triangular polygon, the last one point is repeated to obtain four points of polygon data.

Example) In the case of a quadrilateral polygon

VERTICES (0,1,2,3)

Example) In the case of a triangular polygon

VERTICES (0,1,2,2)

Attribute data

---

ATTR attribute_label = [] = {                                           
        ATTRIBUTE (Plane, Sort, Texture, Color, Gouraud, Mode, Dir, Option),
         ....... .... ..... ... ... ..... ... .....          
                                                                    
        };                                                          
	

ATTR: Attribute　
Plane: Attribute of whether or not there is backside judgment Sort: Representative point of Z sort　
Texture: Texture name (No.)　
Color: Color data　
Gouraud: Gouraud shading attribute Mode: Drawing mode　
Dir: Polygon and texture state Option: Options and other features　

The attribute has the above eight parameters. Here, the symbols that should actually be output for each parameter and their contents are described.

[Plane]

Single_Plane: With backside judgment

Dual_Plane: No backside judgment

[Sort]

SORT_MIN: Recent points

SORT_CEN: Center point

SORT_MAX: Farthest point

SORT_BFR: Displayed in front of the polygon registered immediately before

[Texture]

No_Texture: For polygons

Texture name: For texture (macro showing texture data)

For details, refer to “ Section 4-3 : Texture Data Specifications”.

[Color]

No_Palet: For texture

C_RGB (r, g, b: Color data for polygons
r, g, and b each represent the three primary colors and contain decimal values from 0 to 31.

[Gouraud]

No_Gouraud: No Gouraud

Address: Relative address of Gouraud shading table

[Mode]

group	macro	Contents
[1]	No_Window	Unrestricted in Window (default)
	Window_In	Display inside the Window
	Window_Out	Display outside the window
[2]	MESHoff	Normal display (default)
	MESHon	Display as a mesh
[3]	ECdis	Disable End Code
	ECenb	Enable End Code (default)
[4]	SPdis	Also show transparent pixels (default)
	SPenb	Do not show transparent pixels
[5]	CL16Bnk	16-color color bank mode (default)
	CL16Look	16-color look-up table mode
	CL64Bnk	64 color color bank mode
	CL128Bnk	128 color color bank mode
	CL256Bnk	256 color color bank mode
	CL32KRGB	32768 color RGB mode
[6]	CL_Replace	Overwrite (standard) mode (default)
	CL_Shadow	Shadow mode
	CL_Half	Semi-brightness mode
	CL_Trans	Semi-transparent mode
	CL_Gouraud	Gouraud shading mode

[Dir]

macro	Contents
sprNoflip	Display textures normally
sprHflip	Flip the texture left and right
sprVflip	Flip the texture upside down
sprHVflip	Flip the texture up / down / left / right
sprPorygon	Show polygons
sprPolyLine	Show polyline
sprLine	Display a straight line using the first two points

[Option]

macro	Contents
UseLight	Perform light source calculation
UseClip	Do not display when the vertices go off the screen
UsePalette	Indicates that the polygon color is in palette format

Of the above parameters, Plane , Sort , and Mode can be obtained by specifying the material name in the next section.

PDATA structure

---

PDATA pdata_label [] = {   
       point_label, n1,  
       polygon_label, n2,
       attribute_label  
      };                
	

pdata_label: Indicates the PDATA type address to be passed to SGL.
point_label: Indicates a POINT type address.　
nl: Indicates the number of points.　
polygon_label: Indicates a POLYGON type address.　
n2: Indicates the number of polygons.　
attribute_label: Indicates an ATTR type address.　

---

OBJECT structure

---

OBJECT object_label [] = {   
       pdata_label,       
       TRANSLATION (x, y, z),
       ROTATION (x, y, z),   
       SCALING (x, y, z),    
       object_child,      
       object_sibling,    

pdata_label: Indicates a PDATA type address.　
TRANSLATION: Indicates the amount of movement.　
ROTATION: Indicates the amount of rotation.　
SCALING: Indicates the amount of enlargement.　
object_child: Indicates the OBJECT type address of the child.
object_sibling: Indicates the OBJECT type address of siblings.

See the “design 3” sample source for how to use this structure.

4-2. Material name specifications

The material name has a meaning for each character. The contents will be reflected in the attribute data as it is. The specifications are shown below.

Generally, it is as follows.

[Plane] [Sort] [Mesh] ([] contains one character, and the material name is represented by three characters, for example, "SSN".)

The attributes of each character are

[Plane]

S: Single_Plane

D: Dual_Plane

[Sort]

N: SORT_MIN

C: SORT_CEN

F: SORT_MAX

B: SORT_BFR

[Mesh]

O: MESHon

N: MESHoff

Example) If the material name is "SCN", the attribute data will be

ATTRIBUTE (Single_Plane, SORT_CEN, No_Texture, C_RGB (r, g, b), No_Gouraud, MESHoff, sprNoflip, NoOption)

It will be.

4-3. Texture data specifications

This is the data needed only for textures. The texture name in “Texture” of the attribute data is based on this data.

If the DGT file used as the texture is "sample.dgt",

---

TEXDAT sample [] = {                      
        rgb, rgb, rgb, rgb, rgb, rgb, rgb, rgb
        rgb, rgb, rgb, rgb, rgb, rgb, rgb, rgb
        .............................  
        };                             

TEXTB: Texture table　
sample: Indicates a label with texture data (file name as it is)
hsize, vsize: The size of the texture (hsize is always a multiple of 8)　
bgr: 1 pixel of texture data　

In addition, each of the three primary colors is represented by a value of 0 to 31 in 5 bits.
The data format is as follows.

	B					G					R
1	Four	3	2	1	0	Four	3	2	1	0	Four	3	2	1	0

Example) Suppose that the graphic data file sample.dgt has the texture of 8x2 size white and black checkers as shown in the figure below.

Figure 4-1 Checkered texture

Then the texture data for this texture will be as follows.

---

TEXDAT sample [] = {                                               
        0xffff, 0x8000, 0xffff, 0x8000, 0xffff, 0x8000, 0xffff, 0x8000,
        0x8000,0xffff, 0x8000,0xffff, 0x8000,0xffff, 0x8000,0xffff 
        };                                                      
	

---

The attribute data of the polygon with the material name "SCN" to which this texture is pasted is

ATTRIBUTE (Single_Plane, SORT_CEN, SAMPLE, No_Palet, No_Gouraud, MESHoff, SprNoflip, NoOption)

It will be.

caution

For textures, the H size must be a multiple of 8. This is a limitation due to Satan's hardware specifications.