< 4/86>VDP2 User's Manual/1.4 Priority Function

★ HARDWARE Manual ★ VDP2 User's Manual ★ Chapter 1 VDP2 Functions

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VDP2 User's Manual/Chapter

■1.4 Priority function

There are four types of priority functions in VDP2: priority function, color calculation function, color offset function, and shadow function.

●Priority function

The display priority of sprites and scroll screens is determined by the size of a 3-bit value called the priority number.
Up to eight values can be set for the sprite's priority number, one of which is specified for each character.
The priority number for the scroll screen is usually specified on a per-screen basis. By using the special priority function, you can change the priority by character or dot.

●Color calculation function

The color calculation function is a function that adds the color data of multiple screens to create an effect that makes the background screen appear transparent through the foreground screen. Normally, this is done on two screens, the top image and the second image, but if you use the extended color calculation function, you can do it on up to four screens.
Normally, you specify whether to perform color calculations on a per-surface basis. Sprites can also be specified for each character by setting sprite color calculation conditions. In addition, the scroll screen can be specified in units of characters or dots by using the special color calculation function.
The color calculation ratio for the top image and second image can be specified from 32 levels. Up to eight color calculation ratios can be set for a sprite, one of which is specified for each character. Also, specify the scroll screen in units of planes.
By using the blur calculation function, you can display a specified screen with horizontal blur.

●Color offset function

The color offset function is a function that adds (subtracts) an offset value to the color data on the screen and displays it, and is used for fade-ins and fade-outs. You can specify whether to use the color offset function for each surface.
Up to two color offset values can be set for each RGB color, and which one to use can be specified for each surface.

●Shadow function

The shadow function is a function that puts a shadow in the shape of a sprite character on each screen.
There are two types of sprites that act as shadows, depending on their data: normal shadows and MSB shadows. Normal shadows can only cast shadows on scroll screens. MSB shadows can cast shadows not only on the scroll screen but also on sprites.

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★ HARDWARE Manual ★ VDP2 User's Manual ★ Chapter 1 VDP2 Functions