SCI full-screen scrolling

Scarlatti · Post by **Scarlatti** » Mon Aug 16, 2010 4:00 am

The ScummVM version of SCI seems to choke a little bit when doing full-screen panning and scrolling while using any scaler. It's still smooth, but I wonder if there's a way to make it less processor-intensive. Also, I'm curious about why horizontal scrolling needs more processing power than its vertical counterpart.

Seldon · Post by **Seldon** » Tue Aug 17, 2010 12:38 pm

Due to video memory organization, vertical scrolling is simply operation of copying 1 block of data, while scrolling horizontaly requires to move each line separately.

m_kiewitz · Post by **m_kiewitz** » Tue Aug 17, 2010 2:03 pm

Seldon wrote:Due to video memory organization, vertical scrolling is simply operation of copying 1 block of data, while scrolling horizontaly requires to move each line separately.

In the case of SCI this isn't correct. We are copying rects, when scrolling vertically and horizontally. Sierra SCI is able to scroll only part of the screen.

Seldon · Post by **Seldon** » Tue Aug 17, 2010 9:02 pm

m_kiewitz wrote: In the case of SCI this isn't correct. We are copying rects, when scrolling vertically and horizontally. Sierra SCI is able to scroll only part of the screen.

Now to think about it, you are right, what I wrote reffers rather to games run in native environment (DOS+VGA), and not ScummVM. Secondly I wonder where Scarlatti observed behaviour of vertical scrolling being smoother than horizontal.

Scarlatti · Post by **Scarlatti** » Wed Aug 18, 2010 4:58 am

Seldon wrote:I wonder where Scarlatti observed behaviour of vertical scrolling being smoother than horizontal.

Space Quest 1 VGA remake (Kerona desert) and Space Quest 4 (Xenon sewers).

Scarlatti · Post by **Scarlatti** » Mon Aug 23, 2010 1:32 pm

I guess some developer is doing something with the scrolling recently. It's a bit jerky in the latest builds.

m_kiewitz · Post by **m_kiewitz** » Mon Aug 23, 2010 2:04 pm

Scarlatti wrote:I guess some developer is doing something with the scrolling recently. It's a bit jerky in the latest builds.

Changed it slightly with r52299 again.

we had some issues on some devices, where scrolling was way too slow and issues on other devices, where scrolling was way too fast. It's now syncing itself time-based - so on systems, where the CPU is doing plenty of other things and the scrolling would be slower, we will skip frames.

Scarlatti · Post by **Scarlatti** » Sun Aug 29, 2010 5:47 pm

I saw that m_kiewitz changed the scrolling to another method. It's both smoother and faster now.