GrQuadUtils Namespace Reference

Classes
class	TessellationHelper

Functions
void	ResolveAAType (GrAAType requestedAAType, GrQuadAAFlags requestedEdgeFlags, const GrQuad &quad, GrAAType *outAAType, GrQuadAAFlags *outEdgeFlags)
int	ClipToW0 (DrawQuad *quad, DrawQuad *extraVertices)
bool	CropToRect (const SkRect &cropRect, GrAA cropAA, DrawQuad *quad, bool computeLocal)
bool	WillUseHairline (const GrQuad &quad, GrAAType aaType, GrQuadAAFlags edgeFlags)
void	Outset (const skvx::float4 &edgeDistances, GrQuad *quad)

Function Documentation

ClipToW0()

int GrQuadUtils::ClipToW0	(	DrawQuad *	quad,
		DrawQuad *	extraVertices
	)

Clip the device vertices of 'quad' to be in front of the W = 0 plane (w/in epsilon). The local coordinates will be updated to match the new clipped vertices. This returns the number of clipped quads that need to be drawn: 0 if 'quad' was entirely behind the plane, 1 if 'quad' did not need to be clipped or if 2 or 3 vertices were clipped, or 2 if 'quad' had one vertex clipped (producing a pentagonal shape spanned by 'quad' and 'extraVertices').

Definition at line 399 of file GrQuadUtils.cpp.

                                                      {
    using Vertices = TessellationHelper::Vertices;
 
    SkASSERT(quad && extraVertices);
 
    if (quad->fDevice.quadType() < GrQuad::Type::kPerspective) {
        // W implicitly 1s for each vertex, so nothing to do but draw unmodified 'quad'
        return 1;
    }
 
    mask4 validW = quad->fDevice.w4f() >= SkPathPriv::kW0PlaneDistance;
    if (all(validW)) {
        // Nothing to clip, can proceed normally drawing just 'quad'
        return 1;
    } else if (!any(validW)) {
        // Everything is clipped, so draw nothing
        return 0;
    }
 
    // The clipped local coordinates will most likely not remain rectilinear
    GrQuad::Type localType = quad->fLocal.quadType();
    if (localType < GrQuad::Type::kGeneral) {
        localType = GrQuad::Type::kGeneral;
    }
 
    // If we got here, there are 1, 2, or 3 points behind the w = 0 plane. If 2 or 3 points are
    // clipped we can define a new quad that covers the clipped shape directly. If there's 1 clipped
    // out, the new geometry is a pentagon.
    Vertices v;
    v.reset(quad->fDevice, &quad->fLocal);
 
    int clipCount = (validW[0] ? 0 : 1) + (validW[1] ? 0 : 1) +
                    (validW[2] ? 0 : 1) + (validW[3] ? 0 : 1);
    SkASSERT(clipCount >= 1 && clipCount <= 3);
 
    // FIXME de-duplicate from the projectedBounds() calculations.
    float4 t = (SkPathPriv::kW0PlaneDistance - v.fW) / (next_ccw(v.fW) - v.fW);
 
    Vertices clip;
    clip.fX = (t * next_ccw(v.fX) + (1.f - t) * v.fX);
    clip.fY = (t * next_ccw(v.fY) + (1.f - t) * v.fY);
    clip.fW = SkPathPriv::kW0PlaneDistance;
 
    clip.fU = (t * next_ccw(v.fU) + (1.f - t) * v.fU);
    clip.fV = (t * next_ccw(v.fV) + (1.f - t) * v.fV);
    clip.fR = (t * next_ccw(v.fR) + (1.f - t) * v.fR);
 
    mask4 ccwValid = next_ccw(v.fW) >= SkPathPriv::kW0PlaneDistance;
    mask4 cwValid  = next_cw(v.fW)  >= SkPathPriv::kW0PlaneDistance;
 
    if (clipCount != 1) {
        // Simplest case, replace behind-w0 points with their clipped points by following CCW edge
        // or CW edge, depending on if the edge crosses from neg. to pos. w or pos. to neg.
        SkASSERT(clipCount == 2 || clipCount == 3);
 
        // NOTE: when 3 vertices are clipped, this results in a degenerate quad where one vertex
        // is replicated. This is preferably to inserting a 3rd vertex on the w = 0 intersection
        // line because two parallel edges make inset/outset math unstable for large quads.
        v.fX = if_then_else(validW, v.fX,
                       if_then_else((!ccwValid) & (!cwValid), next_ccw(clip.fX),
                               if_then_else(ccwValid, clip.fX, /* cwValid */ next_cw(clip.fX))));
        v.fY = if_then_else(validW, v.fY,
                       if_then_else((!ccwValid) & (!cwValid), next_ccw(clip.fY),
                               if_then_else(ccwValid, clip.fY, /* cwValid */ next_cw(clip.fY))));
        v.fW = if_then_else(validW, v.fW, clip.fW);
 
        v.fU = if_then_else(validW, v.fU,
                       if_then_else((!ccwValid) & (!cwValid), next_ccw(clip.fU),
                               if_then_else(ccwValid, clip.fU, /* cwValid */ next_cw(clip.fU))));
        v.fV = if_then_else(validW, v.fV,
                       if_then_else((!ccwValid) & (!cwValid), next_ccw(clip.fV),
                               if_then_else(ccwValid, clip.fV, /* cwValid */ next_cw(clip.fV))));
        v.fR = if_then_else(validW, v.fR,
                       if_then_else((!ccwValid) & (!cwValid), next_ccw(clip.fR),
                               if_then_else(ccwValid, clip.fR, /* cwValid */ next_cw(clip.fR))));
 
        // For 2 or 3 clipped vertices, the resulting shape is a quad or a triangle, so it can be
        // entirely represented in 'quad'.
        v.asGrQuads(&quad->fDevice, GrQuad::Type::kPerspective,
                    &quad->fLocal, localType);
        return 1;
    } else {
        // The clipped geometry is a pentagon, so it will be represented as two quads connected by
        // a new non-AA edge. Use the midpoint along one of the unclipped edges as a split vertex.
        Vertices mid;
        mid.fX = 0.5f * (v.fX + next_ccw(v.fX));
        mid.fY = 0.5f * (v.fY + next_ccw(v.fY));
        mid.fW = 0.5f * (v.fW + next_ccw(v.fW));
 
        mid.fU = 0.5f * (v.fU + next_ccw(v.fU));
        mid.fV = 0.5f * (v.fV + next_ccw(v.fV));
        mid.fR = 0.5f * (v.fR + next_ccw(v.fR));
 
        // Make a quad formed by the 2 clipped points, the inserted mid point, and the good vertex
        // that is CCW rotated from the clipped vertex.
        Vertices v2;
        v2.fUVRCount = v.fUVRCount;
        v2.fX = if_then_else((!validW) | (!ccwValid), clip.fX,
                        if_then_else(cwValid, next_cw(mid.fX), v.fX));
        v2.fY = if_then_else((!validW) | (!ccwValid), clip.fY,
                        if_then_else(cwValid, next_cw(mid.fY), v.fY));
        v2.fW = if_then_else((!validW) | (!ccwValid), clip.fW,
                        if_then_else(cwValid, next_cw(mid.fW), v.fW));
 
        v2.fU = if_then_else((!validW) | (!ccwValid), clip.fU,
                        if_then_else(cwValid, next_cw(mid.fU), v.fU));
        v2.fV = if_then_else((!validW) | (!ccwValid), clip.fV,
                        if_then_else(cwValid, next_cw(mid.fV), v.fV));
        v2.fR = if_then_else((!validW) | (!ccwValid), clip.fR,
                        if_then_else(cwValid, next_cw(mid.fR), v.fR));
        // The non-AA edge for this quad is the opposite of the clipped vertex's edge
        GrQuadAAFlags v2EdgeFlag = (!validW[0] ? GrQuadAAFlags::kRight  : // left clipped -> right
                                   (!validW[1] ? GrQuadAAFlags::kTop    : // bottom clipped -> top
                                   (!validW[2] ? GrQuadAAFlags::kBottom : // top clipped -> bottom
                                                 GrQuadAAFlags::kLeft))); // right clipped -> left
        extraVertices->fEdgeFlags = quad->fEdgeFlags & ~v2EdgeFlag;
 
        // Make a quad formed by the remaining two good vertices, one clipped point, and the
        // inserted mid point.
        v.fX = if_then_else(!validW, next_cw(clip.fX),
                       if_then_else(!cwValid, mid.fX, v.fX));
        v.fY = if_then_else(!validW, next_cw(clip.fY),
                       if_then_else(!cwValid, mid.fY, v.fY));
        v.fW = if_then_else(!validW, clip.fW,
                       if_then_else(!cwValid, mid.fW, v.fW));
 
        v.fU = if_then_else(!validW, next_cw(clip.fU),
                       if_then_else(!cwValid, mid.fU, v.fU));
        v.fV = if_then_else(!validW, next_cw(clip.fV),
                       if_then_else(!cwValid, mid.fV, v.fV));
        v.fR = if_then_else(!validW, next_cw(clip.fR),
                       if_then_else(!cwValid, mid.fR, v.fR));
        // The non-AA edge for this quad is the clipped vertex's edge
        GrQuadAAFlags v1EdgeFlag = (!validW[0] ? GrQuadAAFlags::kLeft   :
                                   (!validW[1] ? GrQuadAAFlags::kBottom :
                                   (!validW[2] ? GrQuadAAFlags::kTop    :
                                                 GrQuadAAFlags::kRight)));
 
        v.asGrQuads(&quad->fDevice, GrQuad::Type::kPerspective,
                    &quad->fLocal, localType);
        quad->fEdgeFlags &= ~v1EdgeFlag;
 
        v2.asGrQuads(&extraVertices->fDevice, GrQuad::Type::kPerspective,
                     &extraVertices->fLocal, localType);
        // Caller must draw both 'quad' and 'extraVertices' to cover the clipped geometry
        return 2;
    }
}

CropToRect()

bool GrQuadUtils::CropToRect	(	const SkRect &	cropRect,
		GrAA	cropAA,
		DrawQuad *	quad,
		bool	computeLocal = true
	)

Crops quad to the provided device-space axis-aligned rectangle. If the intersection of this quad (projected) and cropRect results in a quadrilateral, this returns true. If not, this quad may be updated to be a smaller quad of the same type such that its intersection with cropRect is visually the same. This function assumes that the 'quad' coordinates are finite.

The provided edge flags are updated to reflect edges clipped by cropRect (toggling on or off based on cropAA policy). If provided, the local coordinates will be updated to reflect the updated device coordinates of this quad.

If 'computeLocal' is false, the local coordinates in 'quad' will not be modified.

Definition at line 548 of file GrQuadUtils.cpp.

                                                                                        {
    SkASSERT(quad->fDevice.isFinite());
 
    if (quad->fDevice.quadType() == GrQuad::Type::kAxisAligned) {
        // crop_rect and crop_rect_simple keep the rectangles as rectangles, so the intersection
        // of the crop and quad can be calculated exactly. Some care must be taken if the quad
        // is axis-aligned but does not satisfy asRect() due to flips, etc.
        GrQuadAAFlags clippedEdges;
        if (computeLocal) {
            if (is_simple_rect(quad->fDevice) && is_simple_rect(quad->fLocal)) {
                clippedEdges = crop_simple_rect(cropRect, quad->fDevice.xs(), quad->fDevice.ys(),
                                                quad->fLocal.xs(), quad->fLocal.ys());
            } else {
                clippedEdges = crop_rect(cropRect, quad->fDevice.xs(), quad->fDevice.ys(),
                                         quad->fLocal.xs(), quad->fLocal.ys(), quad->fLocal.ws());
            }
        } else {
            if (is_simple_rect(quad->fDevice)) {
                clippedEdges = crop_simple_rect(cropRect, quad->fDevice.xs(), quad->fDevice.ys(),
                                                nullptr, nullptr);
            } else {
                clippedEdges = crop_rect(cropRect, quad->fDevice.xs(), quad->fDevice.ys(),
                                         nullptr, nullptr, nullptr);
            }
        }
 
        // Apply the clipped edge updates to the original edge flags
        if (cropAA == GrAA::kYes) {
            // Turn on all edges that were clipped
            quad->fEdgeFlags |= clippedEdges;
        } else {
            // Turn off all edges that were clipped
            quad->fEdgeFlags &= ~clippedEdges;
        }
        return true;
    }
 
    if (computeLocal || quad->fDevice.quadType() == GrQuad::Type::kPerspective) {
        // FIXME (michaelludwig) Calculate cropped local coordinates when not kAxisAligned
        // FIXME (michaelludwig) crbug.com/1204347 and skbug.com/9906 - disable this when there's
        // perspective; it does not prove numerical robust enough in the wild and should be
        // revisited.
        return false;
    }
 
    float4 devX = quad->fDevice.x4f();
    float4 devY = quad->fDevice.y4f();
 
    float4 clipX = {cropRect.fLeft, cropRect.fLeft, cropRect.fRight, cropRect.fRight};
    float4 clipY = {cropRect.fTop, cropRect.fBottom, cropRect.fTop, cropRect.fBottom};
 
    // Calculate barycentric coordinates for the 4 rect corners in the 2 triangles that the quad
    // is tessellated into when drawn.
    float4 u1, v1, w1;
    float4 u2, v2, w2;
    if (!barycentric_coords(devX[0], devY[0], devX[1], devY[1], devX[2], devY[2], clipX, clipY,
                            &u1, &v1, &w1) ||
        !barycentric_coords(devX[1], devY[1], devX[3], devY[3], devX[2], devY[2], clipX, clipY,
                            &u2, &v2, &w2)) {
        // Bad triangles, skip cropping
        return false;
    }
 
    // clipDevRect is completely inside this quad if each corner is in at least one of two triangles
    mask4 inTri1 = inside_triangle(u1, v1, w1);
    mask4 inTri2 = inside_triangle(u2, v2, w2);
    if (all(inTri1 | inTri2)) {
        // We can crop to exactly the clipDevRect.
        // FIXME (michaelludwig) - there are other ways to have determined quad covering the clip
        // rect, but the barycentric coords will be useful to derive local coordinates in the future
 
        // Since we are cropped to exactly clipDevRect, we have discarded any perspective and the
        // type becomes kRect. If updated locals were requested, they will incorporate perspective.
        // FIXME (michaelludwig) - once we have local coordinates handled, it may be desirable to
        // keep the draw as perspective so that the hardware does perspective interpolation instead
        // of pushing it into a local coord w and having the shader do an extra divide.
        clipX.store(quad->fDevice.xs());
        clipY.store(quad->fDevice.ys());
        quad->fDevice.setQuadType(GrQuad::Type::kAxisAligned);
 
        // Update the edge flags to match the clip setting since all 4 edges have been clipped
        quad->fEdgeFlags = cropAA == GrAA::kYes ? GrQuadAAFlags::kAll : GrQuadAAFlags::kNone;
 
        return true;
    }
 
    // FIXME (michaelludwig) - use TessellationHelper's inset/outset math to move
    // edges to the closest clip corner they are outside of
 
    return false;
}

Outset()

void GrQuadUtils::Outset ( const skvx::float4 &  edgeDistances, GrQuad *  quad  )

inline

Definition at line 222 of file GrQuadUtils.h.

                                                                      {
    TessellationHelper outsetter;
    outsetter.reset(*quad, nullptr);
    outsetter.outset(edgeDistances, quad, nullptr);
}

ResolveAAType()

void GrQuadUtils::ResolveAAType	(	GrAAType	requestedAAType,
		GrQuadAAFlags	requestedEdgeFlags,
		const GrQuad &	quad,
		GrAAType *	outAAType,
		GrQuadAAFlags *	outEdgeFlags
	)

Definition at line 366 of file GrQuadUtils.cpp.

                                                                     {
    // Most cases will keep the requested types unchanged
    *outAAType = requestedAAType;
    *outEdgeFlags = requestedEdgeFlags;
 
    switch (requestedAAType) {
        // When aa type is coverage, disable AA if the edge configuration doesn't actually need it
        case GrAAType::kCoverage:
            if (requestedEdgeFlags == GrQuadAAFlags::kNone) {
                // This can happen when quads are drawn in bulk, where the requestedAAType was
                // conservatively enabled and the edge flags are per-entry.
                *outAAType = GrAAType::kNone;
            } else if (quad.quadType() == GrQuad::Type::kAxisAligned &&
                       !quad.aaHasEffectOnRect(requestedEdgeFlags)) {
                // For coverage AA, if the quad is a rect and AA-enabled edges line up with pixel
                // boundaries, then overall AA and per-edge AA can be completely disabled.
                *outAAType = GrAAType::kNone;
                *outEdgeFlags = GrQuadAAFlags::kNone;
            }
 
            break;
        // For no or msaa anti aliasing, override the edge flags since edge flags only make sense
        // when coverage aa is being used.
        case GrAAType::kNone:
            *outEdgeFlags = GrQuadAAFlags::kNone;
            break;
        case GrAAType::kMSAA:
            *outEdgeFlags = GrQuadAAFlags::kAll;
            break;
    }
}

WillUseHairline()

bool GrQuadUtils::WillUseHairline	(	const GrQuad &	quad,
		GrAAType	aaType,
		GrQuadAAFlags	edgeFlags
	)

Definition at line 640 of file GrQuadUtils.cpp.

                                                                                   {
    if (aaType != GrAAType::kCoverage || edgeFlags != GrQuadAAFlags::kAll) {
        // Non-aa or msaa don't do any outsetting so they will not be hairlined; mixed edge flags
        // could be hairlined in theory, but applying hairline bloat would extend beyond the
        // original tiled shape.
        return false;
    }
 
    if (quad.quadType() == GrQuad::Type::kAxisAligned) {
        // Fast path that avoids computing edge properties via TessellationHelper.
        // Taking the absolute value of the diagonals always produces the minimum of width or
        // height given that this is axis-aligned, regardless of mirror or 90/180-degree rotations.
        float d = std::min(std::abs(quad.x(3) - quad.x(0)), std::abs(quad.y(3) - quad.y(0)));
        return d < 1.f;
    } else {
        TessellationHelper helper;
        helper.reset(quad, nullptr);
        return helper.isSubpixel();
    }
}