Remove noise from orthographic projection raytracing

We generally add some jitter to the raytracing lines in order to smooth
out over multiple iterations some of the imperfections.  However, when
we do this to an orthographic projection (where all lines are parallel
to start, we don't average and just introduce noticeable noise in the
render

Fixes https://gitlab.com/kicad/code/kicad/issues/8863

3d-viewer/3d_rendering/raytracing/render_3d_raytrace_base.cpp

@@ -486,9 +486,12 @@ void RENDER_3D_RAYTRACE_BASE::renderBlockTracing( uint8_t* ptrPBO, signed int iB
     // Initialize ray packets
     const SFVEC2UI& blockPos = m_blockPositions[iBlock];
     const SFVEC2I blockPosI = SFVEC2I( blockPos.x + m_xoffset, blockPos.y + m_yoffset );
+    const SFVEC2F randDisp = ( m_camera.GetProjection() == PROJECTION_TYPE::ORTHO ) ?
+                             SFVEC2F( 0.0f, 0.0f ) :
+                             SFVEC2F( DISP_FACTOR, DISP_FACTOR );
 
-    RAYPACKET blockPacket( m_camera, (SFVEC2F) blockPosI + SFVEC2F( DISP_FACTOR, DISP_FACTOR ),
-                           SFVEC2F( DISP_FACTOR, DISP_FACTOR ) /* Displacement random factor */ );
+    RAYPACKET blockPacket( m_camera, (SFVEC2F) blockPosI + randDisp,
+                           randDisp /* Displacement random factor */ );
 
 
     HITINFO_PACKET hitPacket_X0Y0[RAYPACKET_RAYS_PER_PACKET];
@@ -566,7 +569,7 @@ void RENDER_3D_RAYTRACE_BASE::renderBlockTracing( uint8_t* ptrPBO, signed int iB
         HITINFO_PACKET_init( hitPacket_AA_X1Y1 );
 
         RAYPACKET blockPacket_AA_X1Y1( m_camera, (SFVEC2F) blockPosI + SFVEC2F( 0.5f, 0.5f ),
-                                       SFVEC2F( DISP_FACTOR, DISP_FACTOR ) );
+                                       randDisp );
 
         if( !m_accelerator->Intersect( blockPacket_AA_X1Y1, hitPacket_AA_X1Y1 ) )
         {
@@ -603,16 +606,16 @@ void RENDER_3D_RAYTRACE_BASE::renderBlockTracing( uint8_t* ptrPBO, signed int iB
         RAY blockRayPck_AA_X1Y1_half[RAYPACKET_RAYS_PER_PACKET];
 
         RAYPACKET_InitRays_with2DDisplacement(
-                m_camera, (SFVEC2F) blockPosI + SFVEC2F( 0.5f - DISP_FACTOR, DISP_FACTOR ),
-                SFVEC2F( DISP_FACTOR, DISP_FACTOR ), blockRayPck_AA_X1Y0 );
+                m_camera, (SFVEC2F) blockPosI + SFVEC2F( 0.5f - randDisp.x, randDisp.y ),
+                randDisp, blockRayPck_AA_X1Y0 );
 
         RAYPACKET_InitRays_with2DDisplacement(
-                m_camera, (SFVEC2F) blockPosI + SFVEC2F( DISP_FACTOR, 0.5f - DISP_FACTOR ),
-                SFVEC2F( DISP_FACTOR, DISP_FACTOR ), blockRayPck_AA_X0Y1 );
+                m_camera, (SFVEC2F) blockPosI + SFVEC2F( randDisp.x, 0.5f - randDisp.y ),
+                randDisp, blockRayPck_AA_X0Y1 );
 
         RAYPACKET_InitRays_with2DDisplacement(
-                m_camera, (SFVEC2F) blockPosI + SFVEC2F( 0.25f - DISP_FACTOR, 0.25f - DISP_FACTOR ),
-                SFVEC2F( DISP_FACTOR, DISP_FACTOR ), blockRayPck_AA_X1Y1_half );
+                m_camera, (SFVEC2F) blockPosI + SFVEC2F( 0.25f - randDisp.x, 0.25f - randDisp.y ),
+                randDisp, blockRayPck_AA_X1Y1_half );
 
         renderAntiAliasPackets( bgColor, hitPacket_X0Y0, hitPacket_AA_X1Y1, blockRayPck_AA_X1Y0,
                                 hitColor_AA_X1Y0 );