Hello, I am working on a survival RPG where you will be able to make basicly anything. The thing is that I want to use the correct mass/weight for objects. I have found this site http://www.simetric.co.uk/si_materials.htm which has the mass per vol for a lot of things. I have not been able to find the mass per vol for grass, dry grass, leaves, and dry leaves. Everything else I should be able to figure out from that site. Anyone have any idea of what it is or a website that has it?

What density do you want? I.E. do you want the density of just the grass/leaf itself, or do you want to include the space between multiple blades of grass/leaves?

If you want the density including the space, you'll get different answers depending on how tightly you pack the grass/leaves. It's easier to measure this density, though, as you can put lots of grass/leaves in a plastic bag and find the density of the entire object.

An easy way to measure the density of objects that won't absorb water is to find the mass of the object (with a scale/balance), then to submerge the object in water and measure how much the water level changes. This won't work with grass or leaves because they'll absorb water, but you could put a large quantity of grass/leaves in a plastic bag, submerge it, and find the volume of the entire thing. Doing that way will give you a lower value for density because you'll include the spaces between blades/leaves, though.

Or you could try googling, but I bet you'll mostly find info about how much grass is in a square foot of land, not how much mass is in a cubic foot of grass.

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Original post by nagromo What density do you want? I.E. do you want the density of just the grass/leaf itself, or do you want to include the space between multiple blades of grass/leaves? If you want the density including the space, you'll get different answers depending on how tightly you pack the grass/leaves. It's easier to measure this density, though, as you can put lots of grass/leaves in a plastic bag and find the density of the entire object. An easy way to measure the density of objects that won't absorb water is to find the mass of the object (with a scale/balance), then to submerge the object in water and measure how much the water level changes. This won't work with grass or leaves because they'll absorb water, but you could put a large quantity of grass/leaves in a plastic bag, submerge it, and find the volume of the entire thing. Doing that way will give you a lower value for density because you'll include the spaces between blades/leaves, though. Or you could try googling, but I bet you'll mostly find info about how much grass is in a square foot of land, not how much mass is in a cubic foot of grass.

Those are some good ideas for measuring it. I will probley do that if I can't find density of them.
Ya, googling was the first thing I did. But I didn't get anything close to what I was looking for.

Don't bother using correct masses / weights or densities.

They're not intuitive, and they don't help with inventory management etc.

If you've got a manufacturing process, don't rely on precise measurements - they make managing crafting resources a pain in the backside. Seriously.

It's much better to use real masses / densities as a *guide* for a much cruder and intuitive system, and allow your resources to be tracked by appropriate 'portions' that are used in your crafting processes.

For example:
Two units of iron ore when smelted provide one unit of iron.
Two units of iron ore plus one unit of charcoal produces one unit of steel.

Which is much easier than adjusting a precise quantity of charcoal to introduce to the iron to produce a harder or softer grade steel.

The objective you have to bear in mind is to make the player's inventory (especially for survival RPG / survival horror games) reasonably easy to limit, and reasonably easy for them to organise and understand.

Edit: Oh, and packing has a greater effect on smaller items (like grass leaves). A bin full of tightly compressed grass weighs a lot.

Though it's not always practical to have every object weigh the correct amount, it never hurts to put things into proportion (a useful site for metal properties is http://www.engineersedge.com/manufacturing_menu.shtml). From this we see cast iron has a density of 0.26 lbs/inch^3 whereas carbon steel has a density of 0.28 lbs/inch^3. You probably wouldn't want to use these exact values (as gritty realism is far from fun in most games), but it's good to make carbon steel slightly heavier than cast iron, just to keep the proportions.

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Original post by _winterdyne_ Don't bother using correct masses / weights or densities. They're not intuitive, and they don't help with inventory management etc. If you've got a manufacturing process, don't rely on precise measurements - they make managing crafting resources a pain in the backside. Seriously. It's much better to use real masses / densities as a *guide* for a much cruder and intuitive system, and allow your resources to be tracked by appropriate 'portions' that are used in your crafting processes. For example: Two units of iron ore when smelted provide one unit of iron. Two units of iron ore plus one unit of charcoal produces one unit of steel. Which is much easier than adjusting a precise quantity of charcoal to introduce to the iron to produce a harder or softer grade steel. The objective you have to bear in mind is to make the player's inventory (especially for survival RPG / survival horror games) reasonably easy to limit, and reasonably easy for them to organise and understand. Edit: Oh, and packing has a greater effect on smaller items (like grass leaves). A bin full of tightly compressed grass weighs a lot.

Ya, I totally forgot about having simple units. My plan was to have exactness behind the scenes and have some basic units available to the player. But after thinking about it, just having the simple units will make it easyer and better. So I'm going to go with that. Thanks for reminding me.