+function place_rectangle(resample_effect, resize_effect, padding_effect, x0, y0, x1, y1, screen_width, screen_height, input_width, input_height)
+ local srcx0 = 0.0
+ local srcx1 = 1.0
+ local srcy0 = 0.0
+ local srcy1 = 1.0
+
+ -- Cull.
+ if x0 > screen_width or x1 < 0.0 or y0 > screen_height or y1 < 0.0 then
+ resample_effect:set_int("width", 1)
+ resample_effect:set_int("height", 1)
+ resample_effect:set_float("zoom_x", screen_width)
+ resample_effect:set_float("zoom_y", screen_height)
+ padding_effect:set_int("left", screen_width + 100)
+ padding_effect:set_int("top", screen_height + 100)
+ return
+ end
+
+ -- Clip.
+ if x0 < 0 then
+ srcx0 = -x0 / (x1 - x0)
+ x0 = 0
+ end
+ if y0 < 0 then
+ srcy0 = -y0 / (y1 - y0)
+ y0 = 0
+ end
+ if x1 > screen_width then
+ srcx1 = (screen_width - x0) / (x1 - x0)
+ x1 = screen_width
+ end
+ if y1 > screen_height then
+ srcy1 = (screen_height - y0) / (y1 - y0)
+ y1 = screen_height
+ end
+
+ if resample_effect ~= nil then
+ -- High-quality resampling.
+ local x_subpixel_offset = x0 - math.floor(x0)
+ local y_subpixel_offset = y0 - math.floor(y0)
+
+ -- Resampling must be to an integral number of pixels. Round up,
+ -- and then add an extra pixel so we have some leeway for the border.
+ local width = math.ceil(x1 - x0) + 1
+ local height = math.ceil(y1 - y0) + 1
+ resample_effect:set_int("width", width)
+ resample_effect:set_int("height", height)
+
+ -- Correct the discrepancy with zoom. (This will leave a small
+ -- excess edge of pixels and subpixels, which we'll correct for soon.)
+ local zoom_x = (x1 - x0) / (width * (srcx1 - srcx0))
+ local zoom_y = (y1 - y0) / (height * (srcy1 - srcy0))
+ resample_effect:set_float("zoom_x", zoom_x)
+ resample_effect:set_float("zoom_y", zoom_y)
+ resample_effect:set_float("zoom_center_x", 0.0)
+ resample_effect:set_float("zoom_center_y", 0.0)
+
+ -- Padding must also be to a whole-pixel offset.
+ padding_effect:set_int("left", math.floor(x0))
+ padding_effect:set_int("top", math.floor(y0))
+
+ -- Correct _that_ discrepancy by subpixel offset in the resampling.
+ resample_effect:set_float("left", srcx0 * input_width - x_subpixel_offset / zoom_x)
+ resample_effect:set_float("top", srcy0 * input_height - y_subpixel_offset / zoom_y)
+
+ -- Finally, adjust the border so it is exactly where we want it.
+ padding_effect:set_float("border_offset_left", x_subpixel_offset)
+ padding_effect:set_float("border_offset_right", x1 - (math.floor(x0) + width))
+ padding_effect:set_float("border_offset_top", y_subpixel_offset)
+ padding_effect:set_float("border_offset_bottom", y1 - (math.floor(y0) + height))
+ else
+ -- Lower-quality simple resizing.
+ local width = round(x1 - x0)
+ local height = round(y1 - y0)
+ resize_effect:set_int("width", width)
+ resize_effect:set_int("height", height)
+
+ -- Padding must also be to a whole-pixel offset.
+ padding_effect:set_int("left", math.floor(x0))
+ padding_effect:set_int("top", math.floor(y0))
+ end
+end
+
+-- This is broken, of course (even for positive numbers), but Lua doesn't give us access to real rounding.
+function round(x)
+ return math.floor(x + 0.5)
+end
+
+function lerp(a, b, t)
+ return a + (b - a) * t
+end
+
+function prepare_sbs_chain(chain, t, screen_width, screen_height)
+ chain.input0.input:connect_signal(0)
+ chain.input1.input:connect_signal(1)
+ set_neutral_color(chain.input0.wb_effect, input0_neutral_color)
+ set_neutral_color(chain.input1.wb_effect, input1_neutral_color)
+
+ -- First input is positioned (16,48) from top-left.
+ local width0 = round(848 * screen_width/1280.0)
+ local height0 = round(width0 * 9.0 / 16.0)
+
+ local top0 = 48 * screen_height/720.0
+ local left0 = 16 * screen_width/1280.0
+ local bottom0 = top0 + height0
+ local right0 = left0 + width0
+
+ -- Second input is positioned (16,48) from the bottom-right.
+ local width1 = round(384 * screen_width/1280.0)
+ local height1 = round(216 * screen_height/720.0)
+
+ local bottom1 = screen_height - 48 * screen_height/720.0
+ local right1 = screen_width - 16 * screen_width/1280.0
+ local top1 = bottom1 - height1
+ local left1 = right1 - width1
+
+ -- Interpolate between the fullscreen and side-by-side views.
+ local scale0, tx0, tx0
+ if zoom_poi == INPUT0_SIGNAL_NUM then
+ local new_left0 = lerp(left0, 0, t)
+ local new_right0 = lerp(right0, screen_width, t)
+ local new_top0 = lerp(top0, 0, t)
+ local new_bottom0 = lerp(bottom0, screen_height, t)
+
+ scale0 = (new_right0 - new_left0) / width0 -- Same vertically and horizonally.
+ tx0 = new_left0 - left0 * scale0
+ ty0 = new_top0 - top0 * scale0
+ else
+ local new_left1 = lerp(left1, 0, t)
+ local new_right1 = lerp(right1, screen_width, t)
+ local new_top1 = lerp(top1, 0, t)
+ local new_bottom1 = lerp(bottom1, screen_height, t)
+
+ scale0 = (new_right1 - new_left1) / width1 -- Same vertically and horizonally.
+ tx0 = new_left1 - left1 * scale0
+ ty0 = new_top1 - top1 * scale0
+ end
+
+ top0 = top0 * scale0 + ty0
+ bottom0 = bottom0 * scale0 + ty0
+ left0 = left0 * scale0 + tx0
+ right0 = right0 * scale0 + tx0
+
+ top1 = top1 * scale0 + ty0
+ bottom1 = bottom1 * scale0 + ty0
+ left1 = left1 * scale0 + tx0
+ right1 = right1 * scale0 + tx0
+ place_rectangle(chain.input0.resample_effect, chain.input0.resize_effect, chain.input0.padding_effect, left0, top0, right0, bottom0, screen_width, screen_height, 1280, 720)
+ place_rectangle(chain.input1.resample_effect, chain.input1.resize_effect, chain.input1.padding_effect, left1, top1, right1, bottom1, screen_width, screen_height, 1280, 720)
+end
+
+function set_neutral_color(effect, color)
+ effect:set_vec3("neutral_color", color[1], color[2], color[3])
+end
+
+function set_neutral_color_from_signal(effect, signal)
+ if signal == INPUT0_SIGNAL_NUM then
+ set_neutral_color(effect, input0_neutral_color)
+ else
+ set_neutral_color(effect, input1_neutral_color)
+ end
+end
+
+function calc_fade_progress(t, transition_start, transition_end)
+ local tt = (t - transition_start) / (transition_end - transition_start)
+ if tt < 0.0 then
+ tt = 0.0
+ elseif tt > 1.0 then
+ tt = 1.0
+ end
+
+ -- Make the fade look maybe a tad more natural, by pumping it
+ -- through a sigmoid function.
+ tt = 10.0 * tt - 5.0
+ tt = 1.0 / (1.0 + math.exp(-tt))
+
+ return tt
+end