25  Rendering: Texture and Sprite Data

In this section you’ll explore how DOOM represents and initializes wall textures, sprite patches, and color translation used in rendering. You’ll see the core structs patch_t and texture_t, the initializer R_InitData in r_data.c, how translation tables for player colors are built, and the pic_t struct for flats.

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25.0.1 patch_t

File: linuxdoom-1.10/r_defs.h

// patch_t defines a single graphic patch used for sprites and masked wall segments.
// width/height are the patch size, leftoffset/topoffset position its origin,
// and columnofs[i] gives the byte offset of column i within the patch data
// (column 0 at &columnofs[width]).

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25.0.2 texture_t

File: linuxdoom-1.10/r_data.c

// texture_t combines one or more texpatch_t into a rectangular wall texture.
// name[8] is the texture name, width/height its dimensions,
// patchcount the number of patches, and patches[] the list of origin/patch indices
// used when composing the final texture.

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25.0.3 R_InitData

File: linuxdoom-1.10/r_data.c

// R_InitData sets up all rendering data after WAD I/O. It calls R_InitTextures to parse
// TEXTURE1/2 and build lookup tables, R_InitFlats for floor/ceiling flats,
// R_InitSpriteLumps for sprite headers, and R_InitColormaps for lighting tables.

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25.0.4 R_InitTranslationTables

File: linuxdoom-1.10/r_draw.c

// R_InitTranslationTables allocates three 256-byte-aligned tables and fills them
// so that the green color ramp (indices 0x70–0x7f) can be remapped to gray, brown,
// or red shirt colors for player sprites. All other colors map to themselves.

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25.0.5 pic_t

File: linuxdoom-1.10/d_textur.h

// pic_t models a flat (unmasked floor/ceiling tile) as an 8-bit image block:
// width/height are dimensions and data represents the first pixel,
// with actual pixel data following in memory. Used when loading flats and drawing spans.

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You’ve seen how DOOM’s renderer describes patches and textures, initializes all graphic data including textures, flats, sprites, and colormaps via R_InitData, builds player-color translation tables, and represents flats with pic_t.