// minimum camera distance
static const Standard_Real MIN_DISTANCE = Pow (0.1, ShortRealDigits() - 2);
-
- // z-range tolerance compatible with for floating point.
- static Standard_Real zEpsilon()
- {
- return FLT_EPSILON;
- }
-
- // relative z-range tolerance compatible with for floating point.
- static Standard_Real zEpsilon (const Standard_Real theValue)
- {
- if (theValue == 0)
- {
- return FLT_EPSILON;
- }
- Standard_Real aLogRadix = Log10 (Abs (theValue)) / Log10 (FLT_RADIX);
- Standard_Real aExp = Floor (aLogRadix);
- return FLT_EPSILON * Pow (FLT_RADIX, aExp);
- };
};
// =======================================================================
gp_XYZ Graphic3d_Camera::ViewDimensions() const
{
// view plane dimensions
- Standard_Real aSize = IsOrthographic() ? myScale : (2.0 * Distance() * Tan (DTR_HALF * myFOVy));
- Standard_Real aSizeX, aSizeY;
- if (myAspect > 1.0)
- {
- aSizeX = aSize * myAspect;
- aSizeY = aSize;
- }
- else
- {
- aSizeX = aSize;
- aSizeY = aSize / myAspect;
- }
+ Standard_Real aSizeY = IsOrthographic() ? myScale : (2.0 * Distance() * Tan (DTR_HALF * myFOVy));
+ Standard_Real aSizeX = myAspect * aSizeY;
// and frustum depth
return gp_XYZ (aSizeX, aSizeY, myZFar - myZNear);
Elem_t aZNear = static_cast<Elem_t> (myZNear);
Elem_t aZFar = static_cast<Elem_t> (myZFar);
Elem_t anAspect = static_cast<Elem_t> (myAspect);
- Elem_t aDXHalf = 0.0, aDYHalf = 0.0;
+ Elem_t aDYHalf = 0.0;
if (IsOrthographic())
{
- aDXHalf = aScale * Elem_t (0.5);
aDYHalf = aScale * Elem_t (0.5);
}
else
{
- aDXHalf = aZNear * Elem_t (Tan (DTR_HALF * myFOVy));
aDYHalf = aZNear * Elem_t (Tan (DTR_HALF * myFOVy));
}
- if (anAspect > 1.0)
- {
- aDXHalf *= anAspect;
- }
- else
- {
- aDYHalf /= anAspect;
- }
-
// sets right of frustum based on aspect ratio
+ Elem_t aDXHalf = anAspect * aDYHalf;
Elem_t aLeft = -aDXHalf;
Elem_t aRight = aDXHalf;
Elem_t aBot = -aDYHalf;
{
Standard_ASSERT_RAISE (theScaleFactor > 0.0, "Zero or negative scale factor is not allowed.");
- // Method changes zNear and zFar parameters of camera so as to fit graphical structures
- // by their graphical boundaries. It precisely fits min max boundaries of primary application
- // objects (second argument), while it can sacrifice the real graphical boundaries of the
- // scene with infinite or helper objects (third argument) for the sake of perspective projection.
+ // Method changes ZNear and ZFar planes of camera so as to fit the graphical structures
+ // by their real boundaries (computed ignoring infinite flag) into the viewing volume.
+ // In addition to the graphical boundaries, the usual min max used for fitting perspective
+ // camera. To avoid numeric errors for perspective camera the negative ZNear values are
+ // fixed using tolerance distance, relative to boundaries size. The tolerance distance
+ // should be computed using information on boundaries of primary application actors,
+ // (e.g. representing the displayed model) - to ensure that they are not unreasonably clipped.
+
if (theGraphicBB.IsVoid())
{
- SetZRange (DEFAULT_ZNEAR, DEFAULT_ZFAR);
+ // ShortReal precision factor used to add meaningful tolerance to
+ // ZNear, ZFar values in order to avoid equality after type conversion
+ // to ShortReal matrices type.
+ const Standard_Real aPrecision = 1.0 / Pow (10.0, ShortRealDigits() - 1);
+
+ Standard_Real aZFar = Distance() * 3.0;
+ Standard_Real aZNear = 0.0;
+
+ if (!IsOrthographic())
+ {
+ if (aZFar < aPrecision)
+ {
+ // Invalid case when both values are negative
+ aZNear = aPrecision;
+ aZFar = aPrecision * 2.0;
+ }
+ else if (aZNear < Abs (aZFar) * aPrecision)
+ {
+ // Z is less than 0.0, try to fix it using any appropriate z-scale
+ aZNear = Abs (aZFar) * aPrecision;
+ }
+ }
+
+ SetZRange (aZNear, aZFar);
return;
}
- // Measure depth of boundary points from camera eye.
+ // Measure depth of boundary points from camera eye
NCollection_Sequence<gp_Pnt> aPntsToMeasure;
- Standard_Real aGraphicBB[6];
+ Standard_Real aGraphicBB[6]; // real graphical boundaries (not accounting infinite flag).
theGraphicBB.Get (aGraphicBB[0], aGraphicBB[1], aGraphicBB[2], aGraphicBB[3], aGraphicBB[4], aGraphicBB[5]);
aPntsToMeasure.Append (gp_Pnt (aGraphicBB[0], aGraphicBB[1], aGraphicBB[2]));
if (isFiniteMinMax)
{
- Standard_Real aMinMax[6];
+ Standard_Real aMinMax[6]; // applicative min max boundaries
theMinMax.Get (aMinMax[0], aMinMax[1], aMinMax[2], aMinMax[3], aMinMax[4], aMinMax[5]);
aPntsToMeasure.Append (gp_Pnt (aMinMax[0], aMinMax[1], aMinMax[2]));
aPntsToMeasure.Append (gp_Pnt (aMinMax[3], aMinMax[4], aMinMax[5]));
}
- // Camera eye plane.
+ // Camera eye plane
gp_Dir aCamDir = Direction();
gp_Pnt aCamEye = myEye;
gp_Pln aCamPln (aCamEye, aCamDir);
const gp_XYZ& anAxialScale = myAxialScale;
- // Get minimum and maximum distances to the eye plane.
+ // Get minimum and maximum distances to the eye plane
Standard_Integer aCounter = 0;
NCollection_Sequence<gp_Pnt>::Iterator aPntIt(aPntsToMeasure);
for (; aPntIt.More(); aPntIt.Next())
Standard_Real aDistance = aCamPln.Distance (aMeasurePnt);
- // Check if the camera is intruded into the scene.
+ // Check if the camera is intruded into the scene
if (aCamDir.IsOpposite (gp_Vec (aCamEye, aMeasurePnt), M_PI * 0.5))
{
aDistance *= -1;
}
- // The first eight points are from theGraphicBB, the last eight points are from theMinMax (can be absent).
+ // the first eight points are from theGraphicBB, the last eight points are from theMinMax
+ // (they can be absent).
Standard_Real& aChangeMinDist = aCounter >= 8 ? aModelMinDist : aGraphMinDist;
Standard_Real& aChangeMaxDist = aCounter >= 8 ? aModelMaxDist : aGraphMaxDist;
aChangeMinDist = Min (aDistance, aChangeMinDist);
aCounter++;
}
- // Compute depth of bounding box center.
+ // Compute depth of bounding box center
Standard_Real aMidDepth = (aGraphMinDist + aGraphMaxDist) * 0.5;
Standard_Real aHalfDepth = (aGraphMaxDist - aGraphMinDist) * 0.5;
- // Compute enlarged or shrank near and far z ranges.
- Standard_Real aZNear = aMidDepth - aHalfDepth * theScaleFactor;
- Standard_Real aZFar = aMidDepth + aHalfDepth * theScaleFactor;
+ // ShortReal precision factor used to add meaningful tolerance to
+ // ZNear, ZFar values in order to avoid equality after type conversion
+ // to ShortReal matrices type.
+ const Standard_Real aPrecision = Pow (0.1, ShortRealDigits() - 2);
- if (!IsOrthographic())
- {
- // Everything is behind the perspective camera.
- if (aZFar < zEpsilon())
- {
- SetZRange (DEFAULT_ZNEAR, DEFAULT_ZFAR);
- return;
- }
- }
-
- //
- // Consider clipping errors due to double to single precision floating-point conversion.
- //
-
- // Model to view transformation performs translation of points against eye position
- // in three dimensions. Both point coordinate and eye position values are converted from
- // double to single precision floating point numbers producing conversion errors.
- // Epsilon (Mod) * 3.0 should safely compensate precision error for z coordinate after
- // translation assuming that the:
- // Epsilon (Eye.Mod()) * 3.0 > Epsilon (Eye.X()) + Epsilon (Eye.Y()) + Epsilon (Eye.Z()).
- Standard_Real aEyeConf = 3.0 * zEpsilon (myEye.XYZ().Modulus());
-
- // Model to view transformation performs rotation of points according to view direction.
- // New z coordinate is computed as a multiplication of point's x, y, z coordinates by the
- // "forward" direction vector's x, y, z coordinates. Both point's and "z" direction vector's
- // values are converted from double to single precision floating point numbers producing
- // conversion errors.
- // Epsilon (Mod) * 6.0 should safely compensate the precision errors for the multiplication
- // of point coordinates by direction vector.
- gp_Pnt aGraphicMin = theGraphicBB.CornerMin();
- gp_Pnt aGraphicMax = theGraphicBB.CornerMax();
-
- Standard_Real aModelConf = 6.0 * zEpsilon (aGraphicMin.XYZ().Modulus()) +
- 6.0 * zEpsilon (aGraphicMax.XYZ().Modulus());
-
- // Compensate floating point conversion errors by increasing zNear, zFar to avoid clipping.
- aZNear -= zEpsilon (aZNear) + aEyeConf + aModelConf;
- aZFar += zEpsilon (aZFar) + aEyeConf + aModelConf;
+ // Compute enlarged or shrank near and far z ranges
+ Standard_Real aZNear = aMidDepth - aHalfDepth * theScaleFactor;
+ Standard_Real aZFar = aMidDepth + aHalfDepth * theScaleFactor;
+ aZNear -= aPrecision * 0.5;
+ aZFar += aPrecision * 0.5;
if (!IsOrthographic())
{
- // For perspective projection, the value of z in normalized device coordinates is non-linear
- // function of eye z coordinate. For fixed-point depth representation resolution of z in
- // model-view space will grow towards zFar plane and its scale depends mostly on how far is zNear
- // against camera's eye. The purpose of the code below is to select most appropriate zNear distance
- // to balance between clipping (less zNear, more chances to observe closely small models without clipping)
- // and resolution of depth. A well applicable criteria to this is a ratio between resolution of z at center
- // of model boundaries and the distance to that center point. The ratio is chosen empirically and validated
- // by tests database. It is considered to be ~0.001 (0.1%) for 24 bit depth buffer, for less depth bitness
- // the zNear will be placed similarly giving lower resolution.
- // Approximation of the formula for respectively large z range is:
- // zNear = [z * (1 + k) / (k * c)],
- // where:
- // z - distance to center of model boundaries;
- // k - chosen ratio, c - capacity of depth buffer;
- // k = 0.001, k * c = 1677.216, (1 + k) / (k * c) ~ 5.97E-4
- //
- // The function uses center of model boundaries computed from "theMinMax" boundaries (instead of using real
- // graphical boundaries of all displayed objects). That means that it can sacrifice resolution of presentation
- // of non primary ("infinite") application graphical objects in favor of better perspective projection of the
- // small applicative objects measured with "theMinMax" values.
- Standard_Real aZRange = isFiniteMinMax ? aModelMaxDist - aModelMinDist : aGraphMaxDist - aGraphMinDist;
- Standard_Real aZMin = isFiniteMinMax ? aModelMinDist : aGraphMinDist;
- Standard_Real aZ = aZMin < 0 ? aZRange / 2.0 : aZRange / 2.0 + aZMin;
- Standard_Real aZNearMin = aZ * 5.97E-4;
- if (aZNear < aZNearMin)
+ if (aZFar >= aPrecision)
{
- // Clip zNear according to the minimum value matching the quality.
- aZNear = aZNearMin;
+ // To avoid numeric errors... (See comments in the beginning of the method).
+ // Choose between model distance and graphical distance, as the model boundaries
+ // might be infinite if all structures have infinite flag.
+ const Standard_Real aGraphicDepth = aGraphicMaxDist >= aGraphicMinDist
+ ? aGraphicMaxDist - aGraphicMinDist : RealLast();
+
+ const Standard_Real aModelDepth = aModelMaxDist >= aModelMinDist
+ ? aModelMaxDist - aModelMinDist : RealLast();
+
+ const Standard_Real aMinDepth = Min (aModelDepth, aGraphicDepth);
+ const Standard_Real aZTolerance =
+ Max (Abs (aMinDepth) * aPrecision, aPrecision);
+
+ if (aZNear < aZTolerance)
+ {
+ aZNear = aZTolerance;
+ }
}
- else
+ else // aZFar < aPrecision - Invalid case when both ZNear and ZFar are negative
{
- // Compensate zNear conversion errors for perspective projection.
- aZNear -= aZFar * zEpsilon (aZNear) / (aZFar - zEpsilon (aZNear));
+ aZNear = aPrecision;
+ aZFar = aPrecision * 2.0;
}
+ }
- // Compensate zFar conversion errors for perspective projection.
- aZFar += zEpsilon (aZFar);
-
- // Ensure that after all the zNear is not a negative value.
- if (aZNear < zEpsilon())
- {
- aZNear = zEpsilon();
- }
+ // If range is too small
+ if (aZFar < (aZNear + Abs (aZFar) * aPrecision))
+ {
+ aZFar = aZNear + Abs (aZFar) * aPrecision;
}
SetZRange (aZNear, aZFar);
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