Since the question is not related to any language, I answer from a Javascript perspective.
I implemented the so called "vertical floor/ceiling" technique as well.
But instead of drawing pixels per pixel with ctx.drawImage() I use putImageData.
First I get the data from the tiles I want to render using a temporary canvas:
var tempCanvas = document.createElement('canvas');
var tempCtx = tempCanvas.getContext('2d');
tempCanvas.width = 64;
tempCanvas.height = 64;
var wallsSprite = new Image();
wallsSprite.onload = function () {
tempCtx.drawImage(wallsSprite, 0, 128, 64, 64, 0, 0, 64, 64);
floorData = tempCtx.getImageData(0, 0, 64, 64);
tempCtx.drawImage(wallsSprite, 0, 192, 64, 64, 0, 0, 64, 64);
ceilData = tempCtx.getImageData(0, 0, 64, 64);
}
wallsSprite.src = "./walls_2.png";
I create an empty imageData:
var floorSprite = this.ctx.createImageData(600, 400);
Then I do my "vertical floor/ceiling" raycasting:
//we check if the wall reaches the bottom of the canvas
// this.wallToBorder = (400 - wallHeight) / 2;
if (this.wallToBorder > 0) {
// we calculate how many pixels we have from bottom of wall to border of canvas
var pixelsToBottom = Math.floor(this.wallToBorder);
//we calculate the distance between the first pixel at the bottom of the wall and the player eyes (canvas.height / 2)
var pixelRowHeight = 200 - pixelsToBottom;
// then we loop through every pixels until we reach the border of the canvas
for (let i = pixelRowHeight; i < 200; i += 1) {
// we calculate the straight distance between the player and the pixel
var directDistFloor = (this.screenDist * 200) / (Math.floor(i));
// we calculate it's real world distance with the angle relative to the player
var realDistance = (directDistFloor / Math.cos(this.angleR));
// we calculate it's real world coordinates with the player angle
this.floorPointx = this.player.x + Math.cos(this.angle) * realDistance / (this.screenDist / 100);
this.floorPointy = this.player.y + Math.sin(this.angle) * realDistance / (this.screenDist / 100);
// we map the texture
var textY = Math.floor(this.floorPointx % 64);
var textX = Math.floor(this.floorPointy % 64);
// we modify floorSprite array:
if (floorData && ceilData) {
floorSprite.data[(this.index * 4) + (i + 200) * 4 * 600] = floorData.data[textY * 4 * 64 + textX * 4]
floorSprite.data[(this.index * 4) + (i + 200) * 4 * 600 + 1] = floorData.data[textY * 4 * 64 + textX * 4 + 1]
floorSprite.data[(this.index * 4) + (i + 200) * 4 * 600 + 2] = floorData.data[textY * 4 * 64 + textX * 4 + 2]
floorSprite.data[(this.index * 4) + (i + 200) * 4 * 600 + 3] = 255;
floorSprite.data[(this.index * 4) + (200 - i) * 4 * 600] = ceilData.data[textY * 4 * 64 + textX * 4]
floorSprite.data[(this.index * 4) + (200 - i) * 4 * 600 + 1] = ceilData.data[textY * 4 * 64 + textX * 4 + 1]
floorSprite.data[(this.index * 4) + (200 - i) * 4 * 600 + 2] = ceilData.data[textY * 4 * 64 + textX * 4 + 2]
floorSprite.data[(this.index * 4) + (200 - i) * 4 * 600 + 3] = 255;
}
}
}
}
}
finally we draw the floor and ceiling before the walls are rendered:
this.ctx.putImageData(floorSprite, 0, 0);
The result is super fast since:
- we don't need to calculate ceiling texture coordinates since we deduce them from the floor coordinates.
- we draw the ceiling/floor only once per loop, not pixels per pixel.
- only the pixels that are visible are redrawn so it doesn't
wastes performance on filling up the whole screen with floor and ceiling, and after that it draws walls.
Maybe it could be optimized with mixing horizontal raysting and putImageData put the game speed with wall/ceiling rendering or without is almost the same.
Here is the result
