Add more variable for triangle_drawing

wip-hugo/routines/triangle/triangle.inc

@@ -1,15 +1,25 @@
 ;;; -*- Mode: asm; indent-tabs-mode: t; tab-width: 8 -*-
 
 ;; The triangles 3 corner-positions, they may be in any given order.
+;; This is inputs to the subrotine!
 A_X = $EA
 A_Y = $E9
 B_X = $E8
 B_Y = $E7
 C_X = $E6
 C_Y = $E5
+
+
 ;; Differense in height (after these points have been sorted look in triangle.s for more detail)
 AB = $E4
 BC = $E3
+;; We need some values for Bresenham's line algorithm, see triangle.s and line_down.s
+V_l = $E2    ;16-bit value (uses E3)
+V_r = $E0    ;16-bit value (used E1)
+dy_2_l = $DE ;16-bit value (used DF)
+dy_2_l = $DC ;16-bit value (used DD)
+D_l = $DA    ;16-bit value (uses DB)
+D_r = $D8    ;16-bit value (uses D9)
 
 ;; These come from mem.inc
 ;; Takes up FF - F5

wip-hugo/routines/triangle/triangle.s

@@ -14,7 +14,7 @@
 ;; Each side of the sub-triangle can have 4 posiboul states (look at how line is implemented)
 
 ;;Lets first sort the edges such as
-;; (i) A is at the highest point
+;; (i) A is at the left point
 ;; (ii) B is at the middle point
 ;; (iii) C is at the lowest point
 ;; Lets also calculate the height-differense for the new points:
@@ -25,11 +25,12 @@
         SEC
         LDA B_Y
         SBC A_Y
-        STA AB
         BCC AB_overflow_end
+        STA AB
 ;; A_Y > B_Y
 AB_overflow:
         EOR #$ff ; Fix byte underflow
+        STA AB
         ;; swop A and B
         LDX B_Y
         LDY A_Y
@@ -44,11 +45,12 @@ AB_overflow_end:
         SEC
         LDA C_Y
         SBC B_Y
-        STA BC
         BCC BC_overflow_end
+        STA BC
 ;; B_Y > C_Y
 BC_overflow:
         EOR #$ff ; Fix byte underflow
+        STA BC
         ;; swop A and B
         LDX C_Y
         LDY B_Y

wip-hugo/routines/triangle/upper_triangle.s

@@ -2,10 +2,9 @@
 
 ;; This is a help program for triangle.s to draw the upper triangle
 
-;; We know that (se triangle.inc)
-;; (i) A is at the highest point
-;; (ii) B is at the middle point
-;; (iii) C is at the lowest point
+;; We know that (se triangle.inc) and triangle.s
+;; The upper triangle has hight AB
+;; Its tip is A
 
 ;; This triangle has 10 posibol cases, see table bellow
 ;; ----------------------------------------------------
@@ -24,8 +23,17 @@
 ;; ----------------------------------------------------
 
 .scope upper_triangle
-        LDA #$00
         ;; Lets for the sake of it say its a lr triangle
-        ;; we need to compute  V_l, V_r, dy_2l, dy_2_r, D_l, and D_r
+        ;; lets also say B is on the left and C is on the right
+        ;; we need to compute  V_l, V_r, dy_2_l, dy_2_r, D_l, and D_r
 
+        ;;We need to clear this memory
+        LDA #$00
+        STA V_l + 1
+        STA V_r + 1
+        STA dy_2_l + 1
+        STA dy_2_l + 1
+        STA $FD ; for pixel_draw
+
+        ;; ..
 .endscope