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