veclavtlica
59 lines
1.9 KiB
C
59 lines
1.9 KiB
C
/*
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Geometry rendering.
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*/
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#ifndef COM_GEM_H
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#define COM_GEM_H
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#include "mat.h"
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#include <stdint.h>
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/* Projects vertex position to a clip space via reordered row-major MVP matrix.
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It skips calculation of z depth component, as we assume to never use it.
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Instead, 3rd returned component is w value, for future projection.
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We must never render from inside geometry, as it will break no Z clipping
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assumption (see com_gem_clip_vis_project()).
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*/
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static inline com_vec_t com_gem_vec_project_clip(com_mat_t a, com_vec_t b) {
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com_vec_t result;
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#define CASE(m_c, m_n) \
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result.a[m_c] = (((int64_t)a.a[m_n * 4 + 0] * b.s.x) + \
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((int64_t)a.a[m_n * 4 + 1] * b.s.y) + \
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((int64_t)a.a[m_n * 4 + 2] * b.s.z) + a.a[m_n * 4 + 3]) >> \
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COM_FIX_FRACBITS;
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CASE(0, 0);
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CASE(1, 1);
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CASE(2, 3);
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#undef CASE
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return result;
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}
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/* TODO: Move to separate render-specific file. */
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/* TODO: If we clip test bounding volume of a model first we can skip
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* all clipping whatsoever, which might hold true more often, than the cost of
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* testing the volume. */
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#define COM_GEM_VERTEX_UNCLIPPED (0 << 0)
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#define COM_GEM_VERTEX_CLIPPED_X (1 << 0)
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#define COM_GEM_VERTEX_CLIPPED_Y (1 << 1)
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/* Attempt to project clip space vertex to NDC, reporting which component lies
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* outside of view. Bit test against those per component. This is needed for
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* determining new view-lying clipped triangles. */
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static inline uint8_t com_gem_clip_vis_project(com_vec_t a, com_vec_t *out) {
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uint8_t mask;
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if (a.s.x < -a.s.z || a.s.x > a.s.z)
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mask ^= COM_GEM_VERTEX_CLIPPED_X;
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if (a.s.y < -a.s.z || a.s.y > a.s.z)
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mask ^= COM_GEM_VERTEX_CLIPPED_Y;
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out->a[0] = com_fix_div(a.a[0], a.a[2]);
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out->a[1] = com_fix_div(a.a[1], a.a[2]);
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return mask;
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}
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#endif
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