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The building of Caveman - Part 3 - getting a handle on directx...

Posted by , 02 April 2014 · 1,001 views

The building of Caveman - Part 3 - Getting a handle on directx

Getting up to speed:
So i was going to be using directx and visual studio c++. All fine and good,
but i hadn't written a line of code in something like six years! So, first
came console mode hello world. then came directx fullscren mode and clearscreen.
then came the usual beginning direct programs. draw triangle. draw
textured triangle, etc. took 5 programs over maybe a week to get back up
to speed enough to proceed.

Getting a handle on directx:
The api for the fixed function directx 9 pipeline is not what i'd call clean.
So a thin wrapper api was called for. i did a lot of research in order to figure
out how to make the pipeline run fast. what the pipline likes to see in the way
of calls, and what games tend to do in the way of calls are rather different.
The pipeline likes to draw large numbers of triangles with the same mesh, texture,
material, and other settings all at once. Games however, tend to draw objects
in a scene which can be made up of many different meshes, tetxures, materials,
settings, etc. The solution was a render queue. I call mine the drawlist.

Basic rules to go fast:
as a result of my research on how to make the pipeline scream, the following
mantras were adopted for graphics:
1. one texture per mesh
2. all textures 256x256
1024x1024 backgrounds are the only exception to mantra #2.

Structs, Arrays of structs, Records, Databases, and Lists:
I've disovered that games run on databases. the list of actvie entities is a
database, for example. all content assets of a given type might also be
considered a game datatbase. i usually implement my databases as arrays of
structs. required size is usually known, so a static array of structs is simple,
fast, and adequate. i will usualy refer to them as datbases or lists, rather than
arrays. and i usually call a struct in an array a datbase record. in these posts,
i will use the terms array, list, and database interchangably. and i will use
struct and record interchanably as well.

The drawlist (the render queue):
It was almost 2 years from the time that i wrote the first drawlist code to the
time i first heard the term "render queue". you learn something new every day!
the drawlist is a list of what to draw. you throw meshes (with textures,
materials, transforms, settings, etc) at it, and it draws everything in optimal
order for you. there's not much to it, a struct with all the info to draw a
textured mesh, like meshID, texID, materialID, mWorld, flags for alpha test,
cull, clamp, etc. these are kept in a list. there's also a 3 dimensional index
into the drawlist. its a list of all the textures, and for each texture, a list
of all the meshes that use that texture, and for each mesh, a list of the indices
into the drawlist of the individual records to draw using that mesh and texture.
Drawing calls add a record to the drawlist and its index. draw_drawlist() goes
through the index, drawing everything in (texture, mesh) order. the drawlist
includes a built-in state manager for drawing. the state manager filters out
redundant state changes such as changing mesh, texture, material, or settings,
when they are already set.

so the render queue (drawlist) and the wrapper api made directx petty easy to
work with, and run fast. Now it was time to build the game.

part 2:

part 4:

January 2017 »

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