GLdc/GL/clip.c

#include <float.h>
#include <stdio.h>

#ifdef _arch_dreamcast
#include <dc/pvr.h>
#else
#define PVR_PACK_COLOR(a, r, g, b) {}
#endif

#include "profiler.h"
#include "clip.h"
#include "../containers/aligned_vector.h"


static unsigned char ZCLIP_ENABLED = 1;

unsigned char isClippingEnabled() {
    return ZCLIP_ENABLED;
}

void enableClipping(unsigned char v) {
    ZCLIP_ENABLED = v;
}

void clipLineToNearZ(const ClipVertex* v1, const ClipVertex* v2, ClipVertex* vout, float* t) __attribute__((optimize("fast-math")));
void clipLineToNearZ(const ClipVertex* v1, const ClipVertex* v2, ClipVertex* vout, float* t) {
    const float NEAR_PLANE = 0.2; // FIXME: this needs to be read from the projection matrix.. somehow

    *t = (NEAR_PLANE - v1->w) / (v2->w - v1->w);

    float vec [] = {v2->xyz[0] - v1->xyz[0], v2->xyz[1] - v1->xyz[1], v2->xyz[2] - v1->xyz[2]};

    vout->xyz[0] = v1->xyz[0] + (vec[0] * (*t));
    vout->xyz[1] = v1->xyz[1] + (vec[1] * (*t));
    vout->xyz[2] = v1->xyz[2] + (vec[2] * (*t));
}

static inline void interpolateFloat(const float v1, const float v2, const float t, float* out) {
    float v = v2 - v1;
    *out = (v * t) + v1;
}

static inline void interpolateVec2(const float* v1, const float* v2, const float t, float* out) {
    /* FIXME: SH4 has an asm instruction for this */
    interpolateFloat(v1[0], v2[0], t, &out[0]);
    interpolateFloat(v1[1], v2[1], t, &out[1]);
}

static inline void interpolateVec3(const float* v1, const float* v2, const float t, float* out) {
    /* FIXME: SH4 has an asm instruction for this */

    interpolateFloat(v1[0], v2[0], t, &out[0]);
    interpolateFloat(v1[1], v2[1], t, &out[1]);
    interpolateFloat(v1[2], v2[2], t, &out[2]);
}

static inline void interpolateVec4(const float* v1, const float* v2, const float t, float* out) {
    /* FIXME: SH4 has an asm instruction for this */
    interpolateFloat(v1[0], v2[0], t, &out[0]);
    interpolateFloat(v1[1], v2[1], t, &out[1]);
    interpolateFloat(v1[2], v2[2], t, &out[2]);
    interpolateFloat(v1[3], v2[3], t, &out[3]);
}

static inline void interpolateColour(const uint8_t* v1, const uint8_t* v2, const float t, uint8_t* out) {
    out[0] = v1[0] + (uint32_t) (((float) (v2[0] - v1[0])) * t);
    out[1] = v1[1] + (uint32_t) (((float) (v2[1] - v1[1])) * t);
    out[2] = v1[2] + (uint32_t) (((float) (v2[2] - v1[2])) * t);
    out[3] = v1[3] + (uint32_t) (((float) (v2[3] - v1[3])) * t);
}

const uint32_t VERTEX_CMD_EOL = 0xf0000000;
const uint32_t VERTEX_CMD = 0xe0000000;

void clipTriangleStrip2(AlignedVector* vertices, uint32_t offset) {
    /* Room for clipping 16 triangles */
    typedef struct {
        ClipVertex vertex[3];
        uint8_t visible;
    } Triangle;

    static Triangle TO_CLIP[256];
    static uint8_t CLIP_COUNT = 0;

    CLIP_COUNT = 0;

    uint32_t i = 0;
    /* Skip the header */
    ClipVertex* header = (ClipVertex*) aligned_vector_at(vertices, offset);
    ClipVertex* vertex = header + 1;

    uint32_t count = vertices->size - offset;

    int32_t triangle = 0;

    /* Start at 3 due to the header */
    for(i = 3; i < count; ++i, ++triangle) {
        vertex = aligned_vector_at(vertices, offset + i);

        uint8_t even = (triangle % 2) == 0;
        ClipVertex* v1 = (even) ? vertex - 2 : vertex - 1;
        ClipVertex* v2 = (even) ? vertex - 1 : vertex - 2;
        ClipVertex* v3 = vertex;

        uint8_t visible = ((v1->w > 0) ? 4 : 0) | ((v2->w > 0) ? 2 : 0) | ((v3->w > 0) ? 1 : 0);

        switch(visible) {
            case 0b111:
                /* All visible? Do nothing */
                continue;
            break;
            case 0b000:
                /*
                    It is not possible that this is any trangle except the first
                    in a strip. That's because:
                    - It's either the first triangle submitted
                    - A previous triangle must have been clipped and the strip
                      restarted behind the plane

                    So, we effectively reboot the strip. We mark the first vertex
                    as the end (so it's ignored) then mark the next two as the
                    start of a new strip. Then if the next triangle crosses
                    back into view, we clip correctly. This will potentially
                    result in a bunch of pointlessly submitted vertices.

                    FIXME: Skip submitting those verts
                */

                /* Even though this is always the first in the strip, it can also
                 * be the last */
                if(v3->flags == VERTEX_CMD_EOL) {
                    /* Wipe out the triangle */
                    *v1 = *v2 = *v3 = *header;
                    // fprintf(stderr, "A\n");
                } else {
                    *v1 = *header;
                    ClipVertex tmp = *v2;
                    *v2 = *v3;
                    *v3 = tmp;

                    triangle = -1;
                    v2->flags = VERTEX_CMD;
                    v3->flags = VERTEX_CMD;
                    // fprintf(stderr, "B\n");
                }
            break;
            case 0b100:
            case 0b010:
            case 0b001:
            case 0b101:
            case 0b011:
            case 0b110:
                /* Store the triangle for clipping */
                TO_CLIP[CLIP_COUNT].vertex[0] = *v1;
                TO_CLIP[CLIP_COUNT].vertex[1] = *v2;
                TO_CLIP[CLIP_COUNT].vertex[2] = *v3;
                TO_CLIP[CLIP_COUNT].visible = visible;
                ++CLIP_COUNT;

                /*
                    OK so here's the clever bit. If any triangle except
                    the first or last needs clipping, then the next one does aswell
                    (you can't draw a plane through a single triangle in the middle of a
                    strip, only 2+). This means we can clip in pairs which frees up two
                    vertices in the middle of the strip, which is exactly the space
                    we need to restart the triangle strip after the next triangle
                */
                if(v3->flags == VERTEX_CMD_EOL) {
                    /* Last triangle in strip so end a vertex early */
                    if(triangle == 0) {
                        // Wipe out the triangle completely
                        *v1 = *v2 = *header;
                    } else {
                        // End the strip
                        (vertex - 1)->flags = VERTEX_CMD_EOL;
                    }

                    /* Reapply the header so a subsequent strip works */
                    *vertex = *header;
                    // fprintf(stderr, "C\n");
                } else if(triangle == 0) {
                    /* First triangle in strip, remove first vertex and swap latter two
                       to restart the strip */
                    ClipVertex tmp = *v2;
                    *v2 = *v3;
                    *v3 = tmp;

                    /* We simulate removing the vertex by duplicating the header in v1 */
                    *v1 = *header;
                    v2->flags = VERTEX_CMD;
                    v3->flags = VERTEX_CMD;

                    triangle = -1;
                    // fprintf(stderr, "D\n");
                } else {
                    ClipVertex* v4 = vertex + 1;

                    TO_CLIP[CLIP_COUNT].vertex[0] = *v3;
                    TO_CLIP[CLIP_COUNT].vertex[1] = *v2;
                    TO_CLIP[CLIP_COUNT].vertex[2] = *v4;

                    visible = ((v3->w > 0) ? 4 : 0) | ((v2->w > 0) ? 2 : 0) | ((v4->w > 0) ? 1 : 0);

                    TO_CLIP[CLIP_COUNT].visible = visible;
                    ++CLIP_COUNT;

                    /* Restart strip */
                    triangle = -1;

                    /* Mark the second vertex as the end of the strip */
                    (vertex - 1)->flags = VERTEX_CMD_EOL;

                    if(v4->flags == VERTEX_CMD_EOL) {
                        *vertex = *header;
                        *v4 = *header;
                        // fprintf(stderr, "E\n");

                    } else {
                        /* Swap the next vertices to start a new strip */
                        ClipVertex tmp = *vertex;
                        *vertex = *v4;
                        *v4 = tmp;

                        vertex->flags = VERTEX_CMD;
                        v4->flags = VERTEX_CMD;
                        // fprintf(stderr, "F\n");
                    }

                    i += 1;
                }
            break;
            default:
                break;
        }
    }

    /* Now, clip all the triangles and append them to the output */
    for(i = 0; i < CLIP_COUNT; ++i) {

    }
}

void clipTriangleStrip(const ClipVertex* vertices, const unsigned int count, AlignedVector* outBuffer) __attribute__((optimize("fast-math")));
void clipTriangleStrip(const ClipVertex* vertices, const unsigned int count, AlignedVector* outBuffer) {

    /* Clipping triangle strips is *hard* this is the algorithm we follow:
     *
     * - Treat each triangle in the strip individually.
     * - If we find a triangle that needs clipping, treat it in isolation.
     *   - End the strip at the triangle
     *   - Generate a new single-triangle strip for it
     *   - Begin a new strip for the remainder of the strip
     *
     * There is probably more efficient way but there are so many different cases to handle that it's
     * difficult to even write them down!
     */

    uint32_t i;
    uint32_t stripCount = 2; /* The number of vertices in the source strip so far */

    ClipVertex* thisVertex = vertices + 1;

    for(i = 2; i < count; ++i) {
        ++thisVertex;

        if(stripCount < 2) {
            stripCount++;
            continue;
        }

        const ClipVertex* sourceTriangle[3] = {
            thisVertex - 2,
            thisVertex - 1,
            thisVertex
        };

        /* If we're on an odd vertex, we need to swap the order of the first two vertices, as that's what
         * triangle strips do */
        uint32_t swap = stripCount > 2 && (stripCount % 2 != 0);
        const ClipVertex* v1 = swap ? sourceTriangle[1] : sourceTriangle[0];
        const ClipVertex* v2 = swap ? sourceTriangle[0] : sourceTriangle[1];
        const ClipVertex* v3 = sourceTriangle[2];

        uint32_t visible = ((v1->w > 0) ? 4 : 0) | ((v2->w > 0) ? 2 : 0) | ((v3->w > 0) ? 1 : 0);
        uint32_t startOfStrip = (i == 2) || (outBuffer->size > 2 && ((ClipVertex*) aligned_vector_back(outBuffer))->flags == VERTEX_CMD_EOL);

        /* All visible, we're fine! */
        if(visible == 0b111) {
            if(startOfStrip) {
                aligned_vector_push_back(outBuffer, v1, 1);
                aligned_vector_push_back(outBuffer, v2, 1);
            }

            aligned_vector_push_back(outBuffer, v3, 1);
        } else if(visible == 0b000) {
            /* Do nothing */
            continue;
        } else if(visible == 0b100) {
            /* Only the first vertex is visible */
            float t1 = 0, t2 = 0;

            ClipVertex output[3];

            clipLineToNearZ(v1, v2, &output[1], &t1);
            clipLineToNearZ(v1, v3, &output[2], &t2);

            interpolateFloat(v1->w, v2->w, t1, &output[1].w);
            interpolateFloat(v1->w, v3->w, t2, &output[2].w);

            output[0] = *v1;

            /* Interpolate normals */
            interpolateVec3(v1->nxyz, v2->nxyz, t1, output[1].nxyz);
            interpolateVec3(v1->nxyz, v3->nxyz, t2, output[2].nxyz);

            /* Interpolate texcoords */
            interpolateVec2(v1->uv, v2->uv, t1, output[1].uv);
            interpolateVec2(v1->uv, v3->uv, t2, output[2].uv);

            interpolateVec2(v1->st, v2->st, t1, output[1].st);
            interpolateVec2(v1->st, v3->st, t2, output[2].st);

            interpolateColour(v1->bgra, v2->bgra, t1, output[1].bgra);
            interpolateColour(v1->bgra, v3->bgra, t2, output[2].bgra);

            output[0].flags = VERTEX_CMD;
            output[1].flags = VERTEX_CMD;
            output[2].flags = VERTEX_CMD_EOL;

            aligned_vector_push_back(outBuffer, output, 3);
        } else if(visible == 0b010) {
            /* Only the second vertex is visible */

            float t1 = 0, t2 = 0;

            ClipVertex output[3];

            clipLineToNearZ(v2, v1, &output[0], &t1);
            clipLineToNearZ(v2, v3, &output[2], &t2);

            interpolateFloat(v2->w, v1->w, t1, &output[0].w);
            interpolateFloat(v2->w, v3->w, t2, &output[2].w);

            output[1] = *v2;

            /* Interpolate normals */
            interpolateVec3(v2->nxyz, v1->nxyz, t1, output[0].nxyz);
            interpolateVec3(v2->nxyz, v3->nxyz, t2, output[2].nxyz);

            /* Interpolate texcoords */
            interpolateVec2(v2->uv, v1->uv, t1, output[0].uv);
            interpolateVec2(v2->uv, v3->uv, t2, output[2].uv);

            interpolateVec2(v2->st, v1->st, t1, output[0].st);
            interpolateVec2(v2->st, v3->st, t2, output[2].st);

            interpolateColour(v2->bgra, v1->bgra, t1, output[0].bgra);
            interpolateColour(v2->bgra, v3->bgra, t2, output[2].bgra);

            output[0].flags = VERTEX_CMD;
            output[1].flags = VERTEX_CMD;
            output[2].flags = VERTEX_CMD_EOL;

            aligned_vector_push_back(outBuffer, output, 3);
        } else if(visible == 0b001) {
            /* Only the third vertex is visible */

            float t1 = 0, t2 = 0;

            ClipVertex output[3];

            clipLineToNearZ(v3, v1, &output[0], &t1);
            clipLineToNearZ(v3, v2, &output[1], &t2);

            interpolateFloat(v3->w, v1->w, t1, &output[0].w);
            interpolateFloat(v3->w, v2->w, t2, &output[1].w);

            output[2] = *v3;

            /* Interpolate normals */
            interpolateVec3(v3->nxyz, v1->nxyz, t1, output[0].nxyz);
            interpolateVec3(v3->nxyz, v2->nxyz, t2, output[1].nxyz);

            /* Interpolate texcoords */
            interpolateVec2(v3->uv, v1->uv, t1, output[0].uv);
            interpolateVec2(v3->uv, v2->uv, t2, output[1].uv);

            interpolateVec2(v3->st, v1->st, t1, output[0].st);
            interpolateVec2(v3->st, v2->st, t2, output[1].st);

            interpolateColour(v3->bgra, v1->bgra, t1, output[0].bgra);
            interpolateColour(v3->bgra, v2->bgra, t2, output[1].bgra);

            output[0].flags = VERTEX_CMD;
            output[1].flags = VERTEX_CMD;
            output[2].flags = VERTEX_CMD_EOL;

            aligned_vector_push_back(outBuffer, output, 3);
        } else if(visible == 0b110) {
            /* Third vertex isn't visible */

            float t1 = 0, t2 = 0;

            ClipVertex output[4];

            clipLineToNearZ(v2, v3, &output[2], &t1);
            clipLineToNearZ(v1, v3, &output[3], &t2);

            interpolateFloat(v2->w, v3->w, t1, &output[2].w);
            interpolateFloat(v1->w, v3->w, t2, &output[3].w);

            output[0] = *v1;
            output[1] = *v2;

            /* Interpolate normals */
            interpolateVec3(v2->nxyz, v3->nxyz, t1, output[2].nxyz);
            interpolateVec3(v1->nxyz, v3->nxyz, t2, output[3].nxyz);

            /* Interpolate texcoords */
            interpolateVec2(v2->uv, v3->uv, t1, output[2].uv);
            interpolateVec2(v1->uv, v3->uv, t2, output[3].uv);

            interpolateVec2(v2->st, v3->st, t1, output[2].st);
            interpolateVec2(v1->st, v3->st, t2, output[3].st);

            interpolateColour(v2->bgra, v3->bgra, t1, output[2].bgra);
            interpolateColour(v1->bgra, v3->bgra, t2, output[3].bgra);

            output[0].flags = VERTEX_CMD;
            output[1].flags = VERTEX_CMD;
            output[2].flags = VERTEX_CMD;
            output[3].flags = VERTEX_CMD_EOL;

            aligned_vector_push_back(outBuffer, output, 4);
        } else if(visible == 0b011) {
            /* First vertex isn't visible, so let's clip along the lines to the second and third */
            float t1 = 0, t2 = 0;

            ClipVertex output[4];

            clipLineToNearZ(v1, v2, &output[0], &t1);
            clipLineToNearZ(v1, v3, &output[2], &t2);

            interpolateFloat(v1->w, v2->w, t1, &output[0].w);
            interpolateFloat(v1->w, v3->w, t2, &output[2].w);

            output[1] = *v2;
            output[3] = *v3;

            /* Interpolate normals */
            interpolateVec3(v1->nxyz, v2->nxyz, t1, output[0].nxyz);
            interpolateVec3(v1->nxyz, v3->nxyz, t2, output[2].nxyz);

            /* Interpolate texcoords */
            interpolateVec2(v1->uv, v2->uv, t1, output[0].uv);
            interpolateVec2(v1->uv, v3->uv, t2, output[2].uv);

            interpolateVec2(v1->st, v2->st, t1, output[0].st);
            interpolateVec2(v1->st, v3->st, t2, output[2].st);

            interpolateColour(v1->bgra, v2->bgra, t1, output[0].bgra);
            interpolateColour(v1->bgra, v3->bgra, t2, output[2].bgra);

            output[0].flags = VERTEX_CMD;
            output[1].flags = VERTEX_CMD;
            output[2].flags = VERTEX_CMD;
            output[3].flags = VERTEX_CMD_EOL;

            aligned_vector_push_back(outBuffer, output, 4);
        } else if(visible == 0b101) {
            /* Second vertex isn't visible */
            float t1 = 0, t2 = 0;

            ClipVertex output[4];

            clipLineToNearZ(v1, v2, &output[1], &t1);
            clipLineToNearZ(v3, v2, &output[3], &t2);

            interpolateFloat(v1->w, v2->w, t1, &output[1].w);
            interpolateFloat(v3->w, v2->w, t2, &output[3].w);

            output[0] = *v1;
            output[2] = *v3;

            /* Interpolate normals */
            interpolateVec3(v1->nxyz, v2->nxyz, t1, output[1].nxyz);
            interpolateVec3(v3->nxyz, v2->nxyz, t2, output[3].nxyz);

            /* Interpolate texcoords */
            interpolateVec2(v1->uv, v2->uv, t1, output[1].uv);
            interpolateVec2(v3->uv, v2->uv, t2, output[3].uv);

            interpolateVec2(v1->st, v2->st, t1, output[1].st);
            interpolateVec2(v3->st, v2->st, t2, output[3].st);

            interpolateColour(v1->bgra, v2->bgra, t1, output[1].bgra);
            interpolateColour(v3->bgra, v2->bgra, t2, output[3].bgra);

            output[0].flags = VERTEX_CMD;
            output[1].flags = VERTEX_CMD;
            output[2].flags = VERTEX_CMD;
            output[3].flags = VERTEX_CMD_EOL;

            aligned_vector_push_back(outBuffer, output, 4);
        }

        /* If this vertex was the last in the list, reset the stripCount */
        if(thisVertex->flags == VERTEX_CMD_EOL) {
            stripCount = 0;
        } else {
            stripCount++;
        }

    }
}