Fading Example

Demo

Screenshot

Screen brightness transitions for fade in/out effects.

Learning Objectives

After this lesson, you will understand:

• How SNES screen brightness control works
• Creating smooth fade transitions
• Different fade speeds and styles
• Using fades for scene transitions

Prerequisites

• Completed background examples
• Understanding of VBlank timing

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What This Example Does

Demonstrates multiple fade effects:

• Fade from black to full brightness
• Fade from full brightness to black
• Fast and slow fade speeds
• Button-triggered transitions

Frame 1:    ████████████████  (Black)
Frame 5:    ▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓▓  (25%)
Frame 10:   ░░░░░░░░░░░░░░░░  (50%)
Frame 15:   ▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒▒  (75%)
Frame 20:   [Full Image]      (100%)

Controls:

• Any button: Advance to next fade effect

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Code Type

C with Direct Register Access

Component	Type
Background setup	Library functions
Brightness control	Direct register (REG_INIDISP)
Fade timing	Frame counting with WaitForVBlank()
Input detection	Direct register access

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INIDISP Register

The INIDISP register ($2100) controls screen brightness:

Bits 0-3: Brightness level (0-15)
Bit 4:    Force blank (1 = screen off)
Bits 5-7: Unused

Value	Effect
$00	Brightness 0 (black, screen on)
$0F	Brightness 15 (full)
$80	Force blank (screen completely off)
$8F	Force blank at full brightness

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Basic Fade Implementation

Already in the lib. fadeOut(u8 speed) and fadeIn(u8 speed) are exposed from snes/console.h since v0.20.x — same signature, same semantics as the snippets below. The example calls those directly; the algorithm below is kept for pedagogical purposes so you can see how a fade works on the wire.

Fade In (Black to Full)

void fadeIn(u8 speed) {
    u8 brightness;
 
    for (brightness = 0; brightness <= 15; brightness++) {
        REG_INIDISP = brightness;
 
        /* Wait multiple frames for slower fade */
        for (u8 i = 0; i < speed; i++) {
            WaitForVBlank();
        }
    }
}

Fade Out (Full to Black)

void fadeOut(u8 speed) {
    u8 brightness;
 
    for (brightness = 15; brightness > 0; brightness--) {
        REG_INIDISP = brightness;
 
        for (u8 i = 0; i < speed; i++) {
            WaitForVBlank();
        }
    }
    REG_INIDISP = 0;  /* Ensure fully black */
}

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Fade Speeds

Different speeds for different purposes:

Speed	Frames per step	Total frames	Duration
1	1	15	0.25 sec
2	2	30	0.5 sec
4	4	60	1.0 sec
8	8	120	2.0 sec

Quick Flash

void flash(void) {
    REG_INIDISP = 0x0F;  /* Full white */
    WaitForVBlank();
    WaitForVBlank();
    fadeIn(1);           /* Quick restore */
}

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Scene Transition Pattern

void changeScene(void) {
    /* Fade out current scene */
    fadeOut(2);
 
    /* Force blank for safe VRAM updates */
    REG_INIDISP = INIDISP_FORCE_BLANK;
 
    /* Load new graphics (safe during blank) */
    loadNewBackground();
    loadNewSprites();
 
    /* Fade in new scene */
    fadeIn(2);
}

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Build & Run

cd $OPENSNES_HOME
make -C examples/transitions/fading

Then open fading.sfc in your emulator (Mesen2 recommended).

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Files

File	Purpose
main.c	Fade logic and demo sequence
data.asm	Background graphics
Makefile	Build configuration (LIB_MODULES := console sprite dma input background)

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Exercises

Exercise 1: Smooth Fade

Create smoother fades using sub-frame timing (though limited by 16 brightness levels):

/* Use longer waits between steps */
for (u8 wait = 0; wait < 8; wait++) {
    WaitForVBlank();
}

Exercise 2: Directional Wipe

Combine with window masking for a wipe effect instead of fade.

Exercise 3: Color Fade

Use color math to fade to a specific color instead of black:

colorMathSetFixedColor(r, g, b);
/* Increase color math intensity as brightness drops */

Exercise 4: Pulse Effect

Create a pulsing brightness effect:

static u8 pulse_dir = 1;
static u8 brightness = 8;
 
brightness += pulse_dir;
if (brightness >= 15 || brightness <= 4) {
    pulse_dir = -pulse_dir;
}
REG_INIDISP = brightness;

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Technical Notes

Force Blank vs Brightness 0

• Brightness 0: Screen shows black, but PPU still renders
• Force Blank: PPU stops rendering, VRAM access is safe

Use force blank when updating graphics, brightness 0 for visual fades.

Fade During Gameplay

For in-game fades without stopping action:

1. Use force blank only briefly for VRAM updates
2. Fade brightness while game continues
3. Game logic runs normally during fade

Alternative: Palette Fade

Instead of hardware brightness, modify palette colors:

/* Fade palette toward black */
for (u8 i = 0; i < 256; i++) {
    palette[i] = (palette[i] * fade_level) >> 4;
}
dmaCopyCGram(palette, 0, 512);

This allows fading specific layers independently.

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What's Next?

Mosaic: Mosaic Example - Pixelation transitions

Parallax: Parallax Scrolling - Multi-speed scrolling with HDMA