Common rendering problem with uncapped frame rate in many SDL2 ports
In multiple SDL2 ports, enabling uncapped frame rate/interpolation without VSync results in a bending/warping/skewing of rendered vertical objects when the player's view moves quickly from either physical motion or mouse turning. The warping happens in the direction of motion (move left, top of vertical object leans left and vice versa), and results in a kind of 'leaning tower of Pisa' effect. It is most noticeable when closely facing a wall (such as the first corridor after the starting stairs in MAP01) and strafing side to side whilst running. It is also very noticeable when circle strafing near pillars. The effect *only* occurs in full screen for the ports I've tested, it does not occur in windowed modes. It is much more pronounced than any usual tearing that might occur.
The ports I have tested are:
- Crispy Doom (5.6 to today's daily build of 5.7.2), 5.5 and every version prior does not feature the bug
- PRBoom+ (2.5.1.5.r4526), the SDL1-based 2.5.1.4 does not feature the bug
- Eternity Engine (4.00.00 Völuspá to 4.01.00-pre-918-g981220d0) - Doom Retro (3.5.3) interestingly does not appear to have this problem, much like Crispy 5.5
- GZDoom (4.3.3) similarly functions normally with rendering interpolation enabled and VSync disabled, though it does not use SDL on Windows as far as I am aware The problem does not occur in these ports without using uncapped frame rate/interpolation. It also does not occur when using uncapped frame rate/interpolation in combination with VSync. The issue is that on most of these ports VSync introduces unplayable input delay or other issues. This seems to be a somewhat recent introduction as I didn't come across it a few years ago; also, as I mentioned it doesn't seem to be present in Crispy 5.5 or PRBoom+ 2.5.1.4. All testing performed on a 64 bit Windows 7 SP1 machine with fully updated drivers using a 60 Hz 1920x1080 LCD monitor. Is anyone else experiencing this behavior? Some other posts referencing either the warping or VSync input lag: - These two seem to reference the warping effect
- These reference input lag with VSync enabled
- Crispy Doom (5.6 to today's daily build of 5.7.2), 5.5 and every version prior does not feature the bug
- PRBoom+ (2.5.1.5.r4526), the SDL1-based 2.5.1.4 does not feature the bug
- Eternity Engine (4.00.00 Völuspá to 4.01.00-pre-918-g981220d0) - Doom Retro (3.5.3) interestingly does not appear to have this problem, much like Crispy 5.5
- GZDoom (4.3.3) similarly functions normally with rendering interpolation enabled and VSync disabled, though it does not use SDL on Windows as far as I am aware The problem does not occur in these ports without using uncapped frame rate/interpolation. It also does not occur when using uncapped frame rate/interpolation in combination with VSync. The issue is that on most of these ports VSync introduces unplayable input delay or other issues. This seems to be a somewhat recent introduction as I didn't come across it a few years ago; also, as I mentioned it doesn't seem to be present in Crispy 5.5 or PRBoom+ 2.5.1.4. All testing performed on a 64 bit Windows 7 SP1 machine with fully updated drivers using a 60 Hz 1920x1080 LCD monitor. Is anyone else experiencing this behavior? Some other posts referencing either the warping or VSync input lag: - These two seem to reference the warping effect
- These reference input lag with VSync enabled