GrQuadUtils::TessellationHelper Class Reference

#include <GrQuadUtils.h>

Public Member Functions
void	reset (const GrQuad &deviceQuad, const GrQuad *localQuad)
skvx::float4	inset (const skvx::float4 &edgeDistances, GrQuad *deviceInset, GrQuad *localInset)
void	outset (const skvx::float4 &edgeDistances, GrQuad *deviceOutset, GrQuad *localOutset)
void	getEdgeEquations (skvx::float4 *a, skvx::float4 *b, skvx::float4 *c)
skvx::float4	getEdgeLengths ()
bool	isSubpixel ()

Friends
int	ClipToW0 (DrawQuad *, DrawQuad *)

Detailed Description

Definition at line 55 of file GrQuadUtils.h.

Member Function Documentation

getEdgeEquations()

void GrQuadUtils::TessellationHelper::getEdgeEquations	(	skvx::float4 *	a,
		skvx::float4 *	b,
		skvx::float4 *	c
	)

Definition at line 1178 of file GrQuadUtils.cpp.

                                                                {
    SkASSERT(a && b && c);
    SkASSERT(fVerticesValid);
    const EdgeEquations& eq = this->getEdgeEquations();
    *a = eq.fA;
    *b = eq.fB;
    *c = eq.fC;
}

getEdgeLengths()

skvx::Vec< 4, float > GrQuadUtils::TessellationHelper::getEdgeLengths

(

)

Definition at line 1189 of file GrQuadUtils.cpp.

                                                     {
    SkASSERT(fVerticesValid);
    return 1.f / fEdgeVectors.fInvLengths;
}

inset()

float4 GrQuadUtils::TessellationHelper::inset	(	const skvx::float4 &	edgeDistances,
		GrQuad *	deviceInset,
		GrQuad *	localInset
	)

Definition at line 1138 of file GrQuadUtils.cpp.

                                                                          {
    SkASSERT(fVerticesValid);
 
    Vertices inset = fOriginal;
    const OutsetRequest& request = this->getOutsetRequest(edgeDistances);
    int vertexCount;
    if (request.fInsetDegenerate) {
        vertexCount = this->adjustDegenerateVertices(-request.fEdgeDistances, &inset);
    } else {
        this->adjustVertices(-request.fEdgeDistances, &inset);
        vertexCount = 4;
    }
 
    inset.asGrQuads(deviceInset, fDeviceType, localInset, fLocalType);
    if (vertexCount < 3) {
        // The interior has less than a full pixel's area so estimate reduced coverage using
        // the distance of the inset's projected corners to the original edges.
        return this->getEdgeEquations().estimateCoverage(inset.fX / inset.fW,
                                                         inset.fY / inset.fW);
    } else {
        return 1.f;
    }
}

isSubpixel()

bool GrQuadUtils::TessellationHelper::isSubpixel

(

)

Definition at line 1208 of file GrQuadUtils.cpp.

                                    {
    SkASSERT(fVerticesValid);
    if (fDeviceType <= GrQuad::Type::kRectilinear) {
        // Check the edge lengths, if the shortest is less than 1px it's degenerate, which is the
        // same as if the max 1/length is greater than 1px.
        return any(fEdgeVectors.fInvLengths > 1.f);
    } else {
        // Compute edge equations and then distance from each vertex to the opposite edges.
        return this->getEdgeEquations().isSubpixel(fEdgeVectors.fX2D, fEdgeVectors.fY2D);
    }
}

outset()

void GrQuadUtils::TessellationHelper::outset	(	const skvx::float4 &	edgeDistances,
		GrQuad *	deviceOutset,
		GrQuad *	localOutset
	)

Definition at line 1163 of file GrQuadUtils.cpp.

                                                                           {
    SkASSERT(fVerticesValid);
 
    Vertices outset = fOriginal;
    const OutsetRequest& request = this->getOutsetRequest(edgeDistances);
    if (request.fOutsetDegenerate) {
        this->adjustDegenerateVertices(request.fEdgeDistances, &outset);
    } else {
        this->adjustVertices(request.fEdgeDistances, &outset);
    }
 
    outset.asGrQuads(deviceOutset, fDeviceType, localOutset, fLocalType);
}

reset()

void GrQuadUtils::TessellationHelper::reset	(	const GrQuad &	deviceQuad,
		const GrQuad *	localQuad
	)

Definition at line 1122 of file GrQuadUtils.cpp.

                                                                                {
    // Record basic state that isn't recorded on the Vertices struct itself
    fDeviceType = deviceQuad.quadType();
    fLocalType = localQuad ? localQuad->quadType() : GrQuad::Type::kAxisAligned;
 
    // Reset metadata validity
    fOutsetRequestValid = false;
    fEdgeEquationsValid = false;
 
    // Compute vertex properties that are always needed for a quad, so no point in doing it lazily.
    fOriginal.reset(deviceQuad, localQuad);
    fEdgeVectors.reset(fOriginal.fX, fOriginal.fY, fOriginal.fW, fDeviceType);
 
    fVerticesValid = true;
}

Friends And Related Function Documentation

ClipToW0

int ClipToW0 ( DrawQuad *  , DrawQuad *    )

friend

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;
    }
}

---

The documentation for this class was generated from the following files:

• third_party/skia/src/gpu/ganesh/geometry/GrQuadUtils.h
• third_party/skia/src/gpu/ganesh/geometry/GrQuadUtils.cpp