examples: add triangle

Makefile

@@ -1,24 +1,31 @@
 OPT = -Os
 
+all: cartridge.bin
+
+phony:
+
+arm9/%.bin: phony
+	make -C arm9/ $(notdir $@)
+
+arm7/%.bin: phony
+	make -C arm7/ $(notdir $@)
+
 OBJ = \
 	header.o \
 	arm9/arm9.bin.o \
 	arm7/arm7.bin.o
-
-all: cartridge.bin
-
-arm9/arm9.bin:
-	make -C arm9/
-
-arm7/arm7.bin:
-	make -C arm7/
-
 cartridge.elf: $(OBJ)
 
+TRIANGLE_OBJ = \
+	header.o \
+	arm9/triangle.bin.o \
+	arm7/arm7.bin.o
+triangle.elf: $(TRIANGLE_OBJ)
+
 TARGET = arm-none-eabi-
 AARCH = -march=armv4t -mlittle-endian
 OBJARCH = -O elf32-littlearm -B armv4t
 LDSCRIPT = cartridge.lds
 include common.mk
 
-.PHONY: arm9/arm9.bin arm7/arm7.bin
+.PHONY: phony

arm9/Makefile

@@ -1,5 +1,11 @@
 OPT = -Os
 
+ALL = \
+	arm9.bin \
+	triangle.bin
+
+all: arm9.bin
+
 OBJ = \
 	start.o \
 	main.o \
@@ -8,10 +14,11 @@ OBJ = \
 	../res/bowser.data.o \
 	../res/bowser.data.pal.o
 
-all: arm9.bin
-
 arm9.elf: $(OBJ)
 
+foo = start.o examples/triangle.o
+triangle.elf: $(foo)
+
 CFLAGS += -I../include
 
 include arm9.mk

arm9/examples/triangle.c

@@ -0,0 +1,123 @@
+#include "io_registers.h"
+#include "bits.h"
+
+void main()
+{
+  // power control
+  io_registers.a.POWCNT = 0
+    | POWCNT__lcd_output_destination__a_to_upper__b_to_lower
+    | POWCNT__geometry_engine__enable
+    | POWCNT__rendering_engine__enable
+    | POWCNT__lcd__enable;
+
+  // enable bg0 and 3d graphics
+  io_registers.a.DISPCNT = 0
+    | DISPCNT__display_mode__graphics_display
+    | DISPCNT__bg0__enable
+    | DISPCNT__display_selection_for_bg0__3d_graphics
+    ;
+
+  // clear matrix stack status
+  io_registers.a.GXSTAT |= GXSTAT__matrix_stack_status__overflow_or_underflow;
+
+  // load identity matrices
+  io_registers.a.MTX_MODE = MTX_MODE__matrix_mode__projection;
+  io_registers.a.MTX_IDENTITY = 0;
+
+  io_registers.a.MTX_MODE = MTX_MODE__matrix_mode__position;
+  io_registers.a.MTX_IDENTITY = 0;
+
+  io_registers.a.MTX_MODE = MTX_MODE__matrix_mode__position_and_vector;
+  io_registers.a.MTX_IDENTITY = 0;
+
+  // disable all 3d effects
+  io_registers.a.DISP3DCNT = 0
+    | DISP3DCNT__clear_image__disable
+    | DISP3DCNT__fog_master__disable
+    | DISP3DCNT__edge_marking__disable
+    | DISP3DCNT__anti_aliasing__disable
+    | DISP3DCNT__alpha_blending__disable
+    | DISP3DCNT__alpha_test__disable
+    | DISP3DCNT__texture_mapping__disable;
+
+  // set the 3d clear color to a dark red
+  io_registers.a.CLEAR_COLOR = 0
+    | CLEAR_COLOR__clear_polygon_id(31)
+    | CLEAR_COLOR__alpha_value(31)
+    | CLEAR_COLOR__blue(1)
+    | CLEAR_COLOR__green(1)
+    | CLEAR_COLOR__red(10);
+
+  // set the depth buffer clear value to the maximum value
+  io_registers.a.CLEAR_DEPTH = CLEAR_DEPTH__value(0x7fff);
+
+  // the following polygons are fully opaque and are not
+  // backface-culled
+  io_registers.a.POLYGON_ATTR = 0
+    | POLYGON_ATTR__alpha_value(31)
+    | POLYGON_ATTR__render_front_surface__enable
+    | POLYGON_ATTR__render_back_surface__enable;
+
+  // the 3d viewport is the entire display area
+  io_registers.a.VIEWPORT = 0
+    | VIEWPORT__y2(191)
+    | VIEWPORT__x2(255)
+    | VIEWPORT__y1(0)
+    | VIEWPORT__x1(0);
+
+  // VTX_10 uses signed 4.6 floating point (10 bit)
+  // | 9 | 8 7 6 | 5 4 3 2 1 0 |
+  // | s |  int  | decimal     |
+  int fixed_point_divisor = 64; // == 2⁶
+
+  // equilateral triangle; centered around the display origin in NDC
+  /*
+        A
+       / \
+      B---C
+
+   */
+
+  // fixed point constants; these are converted from floating-point to
+  // integer at compile-time
+  int ax =  0.0           * fixed_point_divisor;
+  int ay =  1.0           * fixed_point_divisor;
+
+  int bx = -0.86602540378 * fixed_point_divisor; // - sqrt(3) / 2
+  int by = -0.5           * fixed_point_divisor;
+
+  int cx =  0.86602540378 * fixed_point_divisor; // + sqrt(3) / 2
+  int cy = -0.5           * fixed_point_divisor;
+
+  int  z =  1.0           * fixed_point_divisor;
+
+  // the following vertices are a triangle
+  io_registers.a.BEGIN_VTXS = BEGIN_VTXS__type__triangle;
+
+  io_registers.a.COLOR = COLOR__blue(31);
+  io_registers.a.VTX_10 = 0
+    | VTX_10__z_coordinate(z)
+    | VTX_10__y_coordinate(ay)
+    | VTX_10__x_coordinate(ax);
+
+  io_registers.a.COLOR = COLOR__green(31);
+  io_registers.a.VTX_10 = 0
+    | VTX_10__z_coordinate(z)
+    | VTX_10__y_coordinate(by)
+    | VTX_10__x_coordinate(bx);
+
+  io_registers.a.COLOR = COLOR__red(31);
+  io_registers.a.VTX_10 = 0
+    | VTX_10__z_coordinate(z)
+    | VTX_10__y_coordinate(cy)
+    | VTX_10__x_coordinate(cx);
+
+  // end of the triangle
+  io_registers.a.END_VTXS = 0;
+
+  // wait for the geometry engine
+  while (io_registers.a.GXSTAT & GXSTAT__geometry_engine_busy);
+
+  // swap buffers
+  io_registers.a.SWAP_BUFFERS = 0;
+}

cartridge.lds

@@ -21,7 +21,7 @@ SECTIONS
 
   .text.arm9 ALIGN(4) :
   {
-    KEEP(*(.data.arm9/arm9.bin))
+    KEEP(*(.data.arm9*.bin))
   } AT>rom
 
   . = 0x02000000 + 0x8000;
@@ -30,7 +30,7 @@ SECTIONS
 
   .text.arm7 ALIGN(4) :
   {
-    KEEP(*(.data.arm7/arm7.bin))
+    KEEP(*(.data.arm7*.bin))
   } AT>rom
 
   /DISCARD/ :

include/bits.h

@@ -164,6 +164,9 @@
 #define MTX_POP__number_of_pops(v) (((v) & 0x3f) << 0)
 #define MTX_STORE__index(v) (((v) & 0x1f) << 0)
 #define MTX_RESTORE__position(v) (((v) & 0x1f) << 0)
+#define COLOR__blue(v) (((v) & 0x1f) << 10)
+#define COLOR__green(v) (((v) & 0x1f) << 5)
+#define COLOR__red(v) (((v) & 0x1f) << 0)
 #define NORMAL__z_component(v) (((v) & 0x3ff) << 20)
 #define NORMAL__y_component(v) (((v) & 0x3ff) << 10)
 #define NORMAL__x_component(v) (((v) & 0x3ff) << 0)

registers/graphics_engine_bits.csv

@@ -183,6 +183,10 @@
 ,,,,,,
 "MTX_RESTORE",,"4-0","position",,"0b11111",
 ,,,,,,
+"COLOR",,"14-10","blue",,"0b11111",
+"COLOR",,"9-5","green",,"0b11111",
+"COLOR",,"4-0","red",,"0b11111",
+,,,,,,
 "NORMAL",,"29-20","z_component",,"0x7ff",
 "NORMAL",,"19-10","y_component",,"0x7ff",
 "NORMAL",,"9-0","x_component",,"0x7ff",