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Correctly compute planet matrix for frustum (Closes: #17) 

Original misbehaviour was caused by the two facts:
- old matrices are row-based (DX style) while Eigen's are colum-based so
  we need to multiply them in an opposite order
- Scaling() is applied to all matrix members while we need just to move
  our camera n relative units, where n = camera position/planet radius

+ remove old irrelevant comment
pull/110/head
Hleb Valoshka 2018-10-28 12:04:50 +03:00
parent f478faa5a4
commit 4ad277ed7a
1 changed files with 5 additions and 54 deletions
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59
src/celengine/render.cpp
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@ -4722,8 +4722,6 @@ void Renderer::renderObject(const Vector3f& pos,
glScale(scaleFactors);
Matrix3f planetRotation = obj.orientation.toRotationMatrix();
Matrix4f planetMat = Matrix4f::Identity();
planetMat.topLeftCorner(3, 3) = planetRotation;
ri.eyeDir_obj = -(planetRotation * pos).normalized();
ri.eyePos_obj = -(planetRotation * (pos.cwiseQuotient(scaleFactors)));
@ -4760,28 +4758,6 @@ void Renderer::renderObject(const Vector3f& pos,
glLightDirection(GL_LIGHT0 + i, ls.lights[i].direction_obj);
// RANT ALERT!
// This sucks, but it's necessary. glScale is used to scale a unit
// sphere up to planet size. Since normals are transformed by the
// inverse transpose of the model matrix, this means they end up
// getting scaled by a factor of 1.0 / planet radius (in km). This
// has terrible effects on lighting: the planet appears almost
// completely dark. To get around this, the GL_rescale_normal
// extension was introduced and eventually incorporated into into the
// OpenGL 1.2 standard. Of course, not everyone implemented this
// incredibly simple and essential little extension. Microsoft is
// notorious for half-assed support of OpenGL, but 3dfx should have
// known better: no Voodoo 1/2/3 drivers seem to support this
// extension. The following is an attempt to get around the problem by
// scaling the light brightness by the planet radius. According to the
// OpenGL spec, this should work fine, as clamping of colors to [0, 1]
// occurs *after* lighting. It works fine on my GeForce3 when I
// disable EXT_rescale_normal, but I'm not certain whether other
// drivers are as well behaved as nVidia's.
//
// Addendum: Unsurprisingly, using color values outside [0, 1] produces
// problems on Savage4 cards.
Vector3f lightColor = light.color.toVector3() * light.irradiance;
glLightColor(GL_LIGHT0 + i, GL_DIFFUSE, lightColor);
glLightColor(GL_LIGHT0 + i, GL_SPECULAR, lightColor);
@ -4798,39 +4774,14 @@ void Renderer::renderObject(const Vector3f& pos,
obj.orientation *
Scaling3f(1.0f / radius);
*/
#if 0
Affine3f invModelView = cameraOrientation.conjugate() *
Translation3f(-pos) *
obj.orientation *
Scaling(1.0f / radius);
Affine3f invModelView = obj.orientation *
Translation3f(-pos / obj.radius) *
cameraOrientation.conjugate();
Matrix4f invMV = invModelView.matrix();
#else
// XXX: HACK! HACK! HACK!
// This code simply tries to emulate the old one.
//
// The problem is that original celestia's Matrix4 (aka Mat4) uses
// row-major memory layout, but Eigen by default uses column-major layout,
// so when later we call Frustum::transform using calculated here invMV
// we use a transposed matrix:
// void
// Frustum::transform(const Mat4f& m)
// {
// Matrix4f m2 = Map<Matrix4f>(&m[0][0]);
// transform(m2);
// }
// Because of that we apply a transpose() to invMV.
// Due to the same column-major vs row-major issue we swap col(3) with row(3).
//
// All that means that the planet rendering code implemented incorrectly.
// If `Affine3f invModelView` from above is used then planets dissappear
// when an observer gets closer to them.
Matrix4f ct = (Translation3f(-pos / radius) * cameraOrientation).matrix();
for (int i=0; i < 3; i++)
std::swap(ct(3, i), ct(i, 3));
Matrix4f planetMat = Matrix4f::Identity();
planetMat.topLeftCorner(3, 3) = planetRotation;
Matrix4f invMV = (ct * planetMat.transpose()).transpose();
#endif
#else
Mat4f planetMat_old(Vec4f(planetMat.col(0).x(), planetMat.col(0).y(), planetMat.col(0).z(), planetMat.col(0).w()),
Vec4f(planetMat.col(1).x(), planetMat.col(1).y(), planetMat.col(1).z(), planetMat.col(1).w()),
Vec4f(planetMat.col(2).x(), planetMat.col(2).y(), planetMat.col(2).z(), planetMat.col(2).w()),