Package org.lwjgl.opengl

Class OVRMultiview

java.lang.Object

org.lwjgl.opengl.OVRMultiview

public class OVRMultiview
extends java.lang.Object

Native bindings to the OVR_multiview extension.

The method of stereo rendering supported in OpenGL is currently achieved by rendering to the two eye buffers sequentially. This typically incurs double the application and driver overhead, despite the fact that the command streams and render states are almost identical.

This extension seeks to address the inefficiency of sequential multiview rendering by adding a means to render to multiple elements of a 2D texture array simultaneously. In multiview rendering, draw calls are instanced into each corresponding element of the texture array. The vertex program uses a new ViewID variable to compute per-view values, typically the vertex position and view-dependent variables like reflection.

The formulation of this extension is high level in order to allow implementation freedom. On existing hardware, applications and drivers can realize the benefits of a single scene traversal, even if all GPU work is fully duplicated per-view. But future support could enable simultaneous rendering via multi-GPU, tile-based architectures could sort geometry into tiles for multiple views in a single pass, and the implementation could even choose to interleave at the fragment level for better texture cache utilization and more coherent fragment shader branching.

The most obvious use case in this model is to support two simultaneous views: one view for each eye. However, we also anticipate a usage where two views are rendered per eye, where one has a wide field of view and the other has a narrow one. The nature of wide field of view planar projection is that the sample density can become unacceptably low in the view direction. By rendering two inset eye views per eye, we can get the required sample density in the center of projection without wasting samples, memory, and time by oversampling in the periphery.

Requires OpenGL 3.0.

Field Summary

Fields

Modifier and Type	Field and Description
static int	GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_BASE_VIEW_INDEX_OVR GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_NUM_VIEWS_OVR Accepted by the pname parameter of GetFramebufferAttachmentParameteriv.
static int	GL_FRAMEBUFFER_INCOMPLETE_VIEW_TARGETS_OVR Returned by CheckFramebufferStatus.
static int	GL_MAX_VIEWS_OVR Accepted by the pname parameter of GetIntegerv.

Method Summary

Modifier and Type	Method and Description
static void	glFramebufferTextureMultiviewOVR(int target, int attachment, int texture, int level, int baseViewIndex, int numViews) Operates similarly to FramebufferTextureLayer, except that baseViewIndex and numViews selects a range of texture array elements that will be targeted when rendering.

Methods inherited from class java.lang.Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_NUM_VIEWS_OVR, GL_FRAMEBUFFER_ATTACHMENT_TEXTURE_BASE_VIEW_INDEX_OVR

Accepted by the pname parameter of GetFramebufferAttachmentParameteriv.

GL_MAX_VIEWS_OVR

Accepted by the pname parameter of GetIntegerv.

GL_FRAMEBUFFER_INCOMPLETE_VIEW_TARGETS_OVR

Returned by CheckFramebufferStatus.

Method Detail

glFramebufferTextureMultiviewOVR

public static void glFramebufferTextureMultiviewOVR(int target,
                                                    int attachment,
                                                    int texture,
                                                    int level,
                                                    int baseViewIndex,
                                                    int numViews)

Operates similarly to FramebufferTextureLayer, except that baseViewIndex and numViews selects a range of texture array elements that will be targeted when rendering.

The command

View( uint id );

does not exist in the GL, but is used here to describe the multi-view functionality in this section. The effect of this hypothetical function is to set the value of the shader built-in input uint gl_ViewID_OVR.

When multi-view rendering is enabled, drawing commands have the same effect as:

for( int i = 0; i < numViews; i++ ) {
    FramebufferTextureLayer( target, attachment, texture, level, baseViewIndex + i );
    View( i );
    <drawing-command>
}

The result is that every drawing command is broadcast into every active view. The shader uses gl_ViewID_OVR to compute view dependent outputs.

The number of views, as specified by numViews, must be the same for all framebuffer attachments points where the value of FRAMEBUFFER_ATTACHMENT_OBJECT_TYPE is not NONE or the framebuffer is incomplete.

In this mode there are several restrictions:

• in vertex shader gl_Position is the only output that can depend on ViewID
• no transform feedback
• no tessellation control or evaluation shaders
• no geometry shader
• no timer query
• occlusion query results must be between max and sum of per-view queries, inclusive

Errors

INVALID_OPERATION is generated by FramebufferTextureMultiviewOVR if target is READ_FRAMEBUFFER.

INVALID_VALUE is generated by FramebufferTextureMultiviewOVR if numViews is less than 1, if numViews is more than MAX_VIEWS_OVR or if (baseViewIndex + numViews) exceeds MAX_ARRAY_TEXTURE_LAYERS.

INVALID_OPERATION is generated if a rendering command is issued and the number of views in the current draw framebuffer is not equal to the number of views declared in the currently bound program.

Parameters:

target - the framebuffer target. One of:

FRAMEBUFFER

READ_FRAMEBUFFER

DRAW_FRAMEBUFFER

attachment - the attachment point of the framebuffer. One of:

COLOR_ATTACHMENT0	COLOR_ATTACHMENT1	COLOR_ATTACHMENT2	COLOR_ATTACHMENT3
COLOR_ATTACHMENT4	COLOR_ATTACHMENT5	COLOR_ATTACHMENT6	COLOR_ATTACHMENT7
COLOR_ATTACHMENT8	COLOR_ATTACHMENT9	COLOR_ATTACHMENT10	COLOR_ATTACHMENT11
COLOR_ATTACHMENT12	COLOR_ATTACHMENT13	COLOR_ATTACHMENT14	COLOR_ATTACHMENT15
COLOR_ATTACHMENT16	COLOR_ATTACHMENT17	COLOR_ATTACHMENT18	COLOR_ATTACHMENT19
COLOR_ATTACHMENT20	COLOR_ATTACHMENT21	COLOR_ATTACHMENT22	COLOR_ATTACHMENT23
COLOR_ATTACHMENT24	COLOR_ATTACHMENT25	COLOR_ATTACHMENT26	COLOR_ATTACHMENT27
COLOR_ATTACHMENT28	COLOR_ATTACHMENT29	COLOR_ATTACHMENT30	COLOR_ATTACHMENT31
DEPTH_ATTACHMENT	STENCIL_ATTACHMENT	DEPTH_STENCIL_ATTACHMENT

texture - the texture object to attach to the framebuffer attachment point named by attachment

level - the mipmap level of texture to attach

baseViewIndex - the base framebuffer texture layer index

numViews - the number of views to target when rendering