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0027925: Visualization - implement order-independent transparency algorithm within rasterization rendering

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Weighted, Blended Order-Independent Transparency algorithm has been added rasterization pipeline.
In contrast to classical blending transparency it makes transparent objects look independent
from point of view. It also gives better depth occlusion when being used together with a weight factor
based on value of a GL depth buffer. The feature supports desktop OpenGL, OpenGL ES 3.0, ANGLE
and can be used together with MSAA on desktop GL.

To be used it require availability of:
1) Shaders pipeline.
2) Floating point color format for framebuffer (GL_ARB_color_buffer_float).
3) Multiple render targets (GL_ARB_draw_buffers).

Patch does not modify API and does not require application porting.
It adds new rendering options to Graphic3d_RenderingParams structure:
a) Transparency method from enumeration.
b) Scalar factor [0-1] controlling influence of a fragment's depth to its visibility.

Patch also simplifies processing of transparent objects for standard method:
rendering priority of transparent graphical structures is managed automatically,
therefore there is no need to care about it at application's side.
This commit is contained in:
apl
2017-04-25 15:10:15 +03:00
committed by bugmaster
parent 9151562167
commit a1073ae267
41 changed files with 1947 additions and 299 deletions
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46
src/OpenGl/OpenGl_CappingAlgo.cxx
View File

@@ -27,14 +27,6 @@ IMPLEMENT_STANDARD_RTTIEXT(OpenGl_CappingAlgoFilter,OpenGl_RenderFilter)
namespace
{
#if !defined(GL_ES_VERSION_2_0)
static const GLint THE_FILLPRIM_FROM = GL_TRIANGLES;
static const GLint THE_FILLPRIM_TO = GL_POLYGON;
#else
static const GLint THE_FILLPRIM_FROM = GL_TRIANGLES;
static const GLint THE_FILLPRIM_TO = GL_TRIANGLE_FAN;
#endif
//! Render infinite capping plane.
//! @param theWorkspace [in] the GL workspace, context state.
//! @param thePlane [in] the graphical plane, for which the capping surface is rendered.
@@ -88,8 +80,14 @@ namespace
theWorkspace->ApplyAspectFace();
// evaluate number of pair faces
glDisable (GL_DEPTH_TEST);
glDepthMask (GL_FALSE);
if (theWorkspace->UseZBuffer())
{
glDisable (GL_DEPTH_TEST);
}
if (theWorkspace->UseDepthWrite())
{
glDepthMask (GL_FALSE);
}
glStencilFunc (GL_ALWAYS, 1, 0x01);
glStencilOp (GL_KEEP, GL_INVERT, GL_INVERT);
@@ -119,10 +117,16 @@ namespace
// render capping plane using the generated stencil mask
glColorMask (GL_TRUE, GL_TRUE, GL_TRUE, GL_TRUE);
glDepthMask (GL_TRUE);
if (theWorkspace->UseDepthWrite())
{
glDepthMask (GL_TRUE);
}
glStencilFunc (GL_EQUAL, 1, 0x01);
glStencilOp (GL_KEEP, GL_KEEP, GL_KEEP);
glEnable (GL_DEPTH_TEST);
if (theWorkspace->UseZBuffer())
{
glEnable (GL_DEPTH_TEST);
}
renderPlane (theWorkspace, thePlane, aRenderPlane->ToUseObjectProperties()
? aGroupIter.Value()->AspectFace()
@@ -160,7 +164,9 @@ void OpenGl_CappingAlgo::RenderCapping (const Handle(OpenGl_Workspace)& theWorks
// replace primitive groups rendering filter
Handle(OpenGl_RenderFilter) aRenderFilter = theWorkspace->GetRenderFilter();
theWorkspace->SetRenderFilter (theWorkspace->DefaultCappingAlgoFilter());
Handle(OpenGl_CappingAlgoFilter) aCappingFilter = theWorkspace->DefaultCappingAlgoFilter();
aCappingFilter->SetPreviousFilter (aRenderFilter);
theWorkspace->SetRenderFilter (aCappingFilter);
// prepare for rendering the clip planes
glEnable (GL_STENCIL_TEST);
@@ -214,10 +220,16 @@ void OpenGl_CappingAlgo::RenderCapping (const Handle(OpenGl_Workspace)& theWorks
// function : CanRender
// purpose :
// =======================================================================
Standard_Boolean OpenGl_CappingAlgoFilter::CanRender (const OpenGl_Element* theElement)
Standard_Boolean OpenGl_CappingAlgoFilter::ShouldRender (const Handle(OpenGl_Workspace)& theWorkspace,
const OpenGl_Element* theGlElement)
{
const OpenGl_PrimitiveArray* aPArray = dynamic_cast<const OpenGl_PrimitiveArray*> (theElement);
if (!myFilter.IsNull() && !myFilter->ShouldRender (theWorkspace, theGlElement))
{
return Standard_False;
}
const OpenGl_PrimitiveArray* aPArray = dynamic_cast<const OpenGl_PrimitiveArray*> (theGlElement);
return aPArray != NULL
&& aPArray->DrawMode() >= THE_FILLPRIM_FROM
&& aPArray->DrawMode() <= THE_FILLPRIM_TO;
&& aPArray->DrawMode() >= OpenGl_PrimitiveArray::THE_FILLPRIM_FROM
&& aPArray->DrawMode() <= OpenGl_PrimitiveArray::THE_FILLPRIM_TO;
}