On Thu, May 10, 2018 at 10:58 AM, Roland Scheidegger <srol...@vmware.com> wrote:
> Am 10.05.2018 um 16:47 schrieb Ivan Kalvachev: > > On 5/10/18, Roland Scheidegger <srol...@vmware.com> wrote: > >> Quite a sneaky little bug, can't hurt to make undefined behavior a bit > >> more defined :-). > > > > Actually, this behavior is completely defined in Direct3D, > > where out-of-bound access is expected to > > always return 0.0 . > > This is why Witcher1 has the issue in both Gallium Nine and WineD3D > OpenGL. > > (Curiously, only the Linux native OpenGL version of Trine1 EE has that > issue.) > > > > In OpenGL there is "ARB_robust_buffer_access_behavior" > > that Mesa3D claims to support. > > https://urldefense.proofpoint.com/v2/url?u=https-3A__www. > khronos.org_registry_OpenGL_extensions_ARB_ARB-5Frobust- > 5Fbuffer-5Faccess-5Fbehavior.txt&d=DwIBaQ&c=uilaK90D4TOVoH58JNXRgQ&r=_ > QIjpv-UJ77xEQY8fIYoQtr5qv8wKrPJc7v7_-CYAb0&m= > HABSbOZm1CI6dmKtNDRaqMEehdOkLSLHDcqhAPZECQo&s=IUJuFond_Xq02RLZJgY8K1CFlBF_ > pojvx3uMNzW113Q&e= > > > > Here is a quote that might be relevant to these cases: > > --- > > Add to Section 2.8 "Vertex Arrays" before 2.8.1 (Packed Vertex Data > > Formats): > > > > "Robust buffer access can be enabled by creating a context with > robust > > access enabled through the window system binding APIs. When enabled, > > indices within the elements array that reference vertex data that > > lies outside the enabled attributes vertex buffer objects, result in > > reading zero.[...] > > --- > > Vertex arrays. > Buffer objects in general (such as for uniform buffers) can still return > just about anything (albeit not allowed to be data from outside the > buffer, either 0 or any value from inside the buffer). (And for > out-of-bounds it even considers the full buffer, not the bound buffer > range). So a test checking for conformance there wouldn't help. > The Witcher1 issue isn't even about buffers. It uses out-of-bounds indexing on uniform arrays. So ARB_robust_buffer_access_behavior doesn't apply. Marek
_______________________________________________ mesa-dev mailing list mesa-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/mesa-dev
