zarchy-engine

An engine to simulate the visuals of the game zarch/virus, made for the pico-8!

Docs

Load main.p8. The sample "game" is in game.lua. What you need to know:

How to import - into pico-8 memory - terrain heightmap, terrain objects and polygons

• Requirements:
  • A square png image for the terrain heightmap. You can use only the three first pico-8 colors in this: #000000, #1d2b53, #7e2553. They represent: water, land, high land. See test.png for reference
  • A square png image for the terrain objects. You can use all 16 pico-8 colors from standard pallete (meaning you can have up to 16 different terrain objects, like trees and houses). Color #000000 means "no objects in this position". See objs.png for reference.
  • A txt file with vertices and faces data, 3 lines for each model. Follow the format:

(v1_x,v1_y,v1_z),(v2_x,v2_y,v2_z),(v3_x,v3_y,v3_z), ...
(v1,v2,v3,color), ...
(offset_x,offset_y,offset_z,scale)

(v1_x,v1_y,v1_z),(v2_x,v2_y,v2_z),(v3_x,v3_y,v3_z), ...
(v1,v2,v3,color), ...
(offset_x,offset_y,offset_z,scale)

• To get data to import into pico-8:
  • Run get_gfx.bat to extract bytes from the sample images (test.png, objs.png and model.txt).
  • Type the following command, with your custom images, in cmd: py pico8rle.py [terrain_image].png --models [models_image].txt --objs [objects_image].png
• Finally
  • Run the command above
  • Keep note of the numbers at the start (these are the memory positions of the terrain, terrain objects and polygons
  • Copy everything from __gfx__ on into main.p8.

How to instantiate objects and particles

• In game.lua, make sure you populate OBJS_DATA with {decode_model(memlocation_obj1), decode_model(memlocation_obj2)...}
• Use create_object3d and add it to game_objects3d to instantiate 3D objects.
  • Make sure you fill at least the first 4 parameters: obj_id,x,y,z. obj_id is the array index of the polygon this object will instantiate. Aditionally, you can set a update_func (a function that updates the logic of the object every frame) or start_func (a function which only runs when the object is created).
• Use create_sprite3d and add it to game_objects3d to instantiate sprites/particles.
  • Sprites have many parameters, such as x,y,z,draw_func (the function that draws the shape, like rectfill), update_func (a function that updates the logic the object every frame), start_func (a function which only runs when sprite is created), vx,vy,vz, life_span (how much the sprite will last on screen)
• To simulate gravity, you can set update_func to gravity which is a helper function located in zarchy_engine.lua

Other parameters

• zarchy_engine.lua
  • HEIGHTMULTIPLIER
  • TILE_SIZE
  • NUMSECTS
  • K_SCREEN_SCALE,K_X_CENTER,K_Y_CENTER,Z_CLIP,Z_MAX
  • CAM_DIST_TERRAIN
• decoders.lua
  • NUM_PASSES
  • TERRAIN_MEMLOC_START
  • OBJS_MEMLOC_END
• game.lua
  • OBJS_DATA