cgv::render::gl::gl_transparent_renderer Class Reference

#include <gl_transparent_renderer.h>

Inheritance diagram for cgv::render::gl::gl_transparent_renderer:

Public Member Functions
	gl_transparent_renderer (bool front_to_back=true, float _depth_bias=0.001)
	construct uninitialized depth peeler
bool	init (context &ctx)
	checks for extensions and init depth peeler, return success
void	init_frame (context &ctx)
	configure frame buffer and textures
int	render_transparent (context &ctx, int max_nr_layers, int tex_unit=-1)
	perform transparent rendering by considering a maximum of the specified number of depth layers
void	destruct (context &ctx)
	destruct the transparent renderer
void	invert_t (bool enable=true)
	set the sign for the vertical texture coordinate. In case of some ATI-cards this needs to be enabled to avoid flipping intermediate textures. More...
void	set_back_to_front ()
	enable back to front mode
void	set_front_to_back ()
	enable front to back mode
bool	is_front_to_back () const
	return whether the mode is front to back
void	set_depth_bias (float bias)
	the depth bias is used as epsilon for the test against the second depth buffer and is initialized to 0.0005f
float	get_depth_bias () const
	return the current depth bias
bool	is_initialized () const
	check whether the depth peeler has been initialized, i.e. the init method has been called successfully before
void	copy_depth_buffer (context &ctx)
	copies the current depth buffer to the second depth buffer, what is typically done before peeling a layer
void	begin_layer (context &ctx, int tex_unit=-1)
	start to extract the next layer. Within begin_layer and end_layer the following OpenGL features are used: texture generation functions, 2D texturing and the alpha Test
unsigned int	end_layer (context &ctx)
	finish the layer and return the number of drawn fragments in the layer. All OpenGL settings are restored. More...

Public Attributes
std::string	last_error
	a string that contains the last error, which is only set by the init method
cgv::signal::signal< context & >	render_callback
	signal called to render the transparent content for first layer without additional depth test
cgv::signal::signal< context &, texture & >	render_callback_2
	signal called to render the transparent content for second and further layers with additional depth test against texture given in second argument

Protected Member Functions
void	create_and_attach_texture (context &ctx, texture &tex, int w, int h, int i=-1)
	ensure that texture has the correct dimensions and is created
void	blend_texture_over_viewport (context &ctx, texture &tex)
	renders the given texture over the current viewport

Protected Attributes
gl_depth_peeler	peeler
	depth peeler used for visibility sorting
texture	color_tex
	texture used as color buffer in front to back mode to blend together all transparent layers before blending the result over the current color buffer

Detailed Description

OpenGL helper class to simplify transparent rendering. It is derived from a depth peeler whose functionality is used for the visibility sorting according to the approach described in the "order independent transparency" paper of Cass Everit. Call the init method after your OpenGL context has been created. Transparent rendering is done such that the rendered objects are blended over the rendered scene in the current color and depth buffer. Rendering of transparent objects should be done in the finish_frame method of a drawable. A sample implementation looks like this:

// in init

Member Function Documentation

end_layer()

unsigned int cgv::render::gl::gl_depth_peeler::end_layer ( context &  ctx )

inherited

finish the layer and return the number of drawn fragments in the layer. All OpenGL settings are restored.

finish the layer and return the number of drawn fragments in the layer

invert_t()

void cgv::render::gl::gl_depth_peeler::invert_t ( bool  enable = true )

inherited

set the sign for the vertical texture coordinate. In case of some ATI-cards this needs to be enabled to avoid flipping intermediate textures.

set the sign for y

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

• D:/develop/projects/git/cgv/libs/cgv_gl/gl/gl_transparent_renderer.h
• D:/develop/projects/git/cgv/libs/cgv_gl/gl/gl_transparent_renderer.cxx