Robert Allan James
ef9806977a
Adds Module 28 (framebuffer_words.c/.h): PLOT ( x y color -- ), FB-WIDTH, FB-HEIGHT -- raw hardware-boundary C primitives, kernel-only, no-op on hosted builds, same pattern as every other module. Adds capsules/fabric.4th (blocks 4900-4902, mkcapsule --lint clean): COS45/Z->DELTA/PROJECT/CART-Y/CART-PLOT -- the 45-degree cavalier orthographic projection and Y-flip, in FORTH per the compose-in-FORTH-first rule (this is policy, not hardware access). Found and fixed a second real bug while live-testing CART-PLOT over the serial socket: defining_word_variable() (defining_words.c) captured vm->here as a VARIABLE's address with no alignment call first, while vm_load_cell/vm_store_cell require 8-byte-aligned addresses. This capsule's VARIABLE ZD landed misaligned (945) purely by chance of what preceded it; other capsules' variables happened to land aligned by luck, not guarantee. Real deviation from FORTH-83/ANS, which specifies VARIABLE reserves an aligned cell. Fixed with vm_align(vm) before capturing addr -- ALIGN already existed as a word but VARIABLE wasn't calling it. Verified end-to-end on amd64 via manual serial injection + QEMU screendump: plotted 4 marker points (origin, +100 X, +100 Y, +50 Z) and confirmed all landed at hand-calculated raster coordinates, including the diagonal up-right shift for the Z-axis point -- the projection math is correct, not just non-crashing. fb/fabric-test-cart-plot.png. 4.3.1's corner diagnostic still renders correctly in the same shot, confirming no regression. All three architectures (amd64/aarch64/riscv64) boot clean to ok> with the DoE completing; dict_hash identical across all three (0xc7f9adf885e306d2), confirming parity is unaffected. FABRIC.md item 4.3.3 marked done with full acceptance evidence.
33 lines
992 B
Forth
33 lines
992 B
Forth
Block 4900
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( fabric.4th -- Console drawing-fabric coordinate machinery )
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( FABRIC.md item 4.3.3. 45-degree cavalier orthographic )
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( projection. Z is depth-into-screen, not height. Q48.16 )
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( throughout. Raw pixel write (PLOT/FB-WIDTH/FB-HEIGHT) is )
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( C; this capsule is the FORTH-side policy on top of it. )
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46341 CONSTANT COS45 ( Q48.16 cos(45)=sin(45) ~= 0.70710678 )
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VARIABLE ZD
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: Z->DELTA ( z -- delta )
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Q.FROM-INT COS45 Q.* Q.TO-INT ;
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Block 4901
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( PROJECT: 3D Cartesian (x y z) -> 2D Cartesian (sx sy). )
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( Cavalier projection: depth pushes diagonally up-right. )
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: PROJECT ( x y z -- sx sy )
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Z->DELTA ZD !
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ZD @ +
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SWAP ZD @ +
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SWAP ;
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( CART-Y: Cartesian Y (origin bottom, up positive) -> )
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( raster Y (origin top, down positive). The Y-flip. )
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: CART-Y ( cart-y -- raster-y )
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FB-HEIGHT 1- SWAP - ;
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Block 4902
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( CART-PLOT: full pipeline -- 3D Cartesian point to screen. )
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: CART-PLOT ( x y z color -- )
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>R
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PROJECT
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CART-Y
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R>
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PLOT ;
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